Add multilingual language and systems learning tracks

en/ruby-foundations-20261101/README.md

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+# Ruby — first steps
+
+[Agila University track](https://edu.agilaos.com/track.php?track=19&lang=en)
+
+About 15 minutes per lesson. Predict, run, change, explain, then complete the check in University.
+
+- [Lesson 1: Your first explainable program](lesson-1/lesson.html)
+- [Lesson 2: Values and decisions](lesson-2/lesson.html)
+- [Lesson 3: Functions and a clear policy](lesson-3/lesson.html)

en/ruby-foundations-20261101/lesson-1/lesson.html

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+<!doctype html><html lang="en"><meta charset="utf-8"><title>Your first explainable program</title><h1>Your first explainable program</h1><p>15-minute session: read for 3 minutes, trace for 3, experiment for 7, and complete the check for 2. Spend longer whenever you need.</p><p>A program is a set of instructions. Read the example from its entry point to the output statement. Text in quotes is data; the output operation is an instruction. Predict the printed line before running. Change only the message, run again, then remove one required punctuation mark and read the first error. Restore the working source.</p><p><code>puts</code> prints a line. <code>def</code> and <code>end</code> delimit a method. <code>each</code> yields values to a block. An instance variable beginning with <code>@</code> belongs to an object; two objects can hold different values.</p><pre><code class="language-ruby">puts &quot;Ready&quot;
+</code></pre><p><strong>Expected result:</strong> <code>Ready</code></p><h3>Practice and evidence</h3><p>Keep three notes: your prediction, the actual result, and why they match or differ. The completion check grades understanding; the practice task builds skill.</p><p><a href="https://www.ruby-lang.org/en/documentation/">Language reference</a></p></html>

en/ruby-foundations-20261101/lesson-1/main.rb

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+puts "Ready"

en/ruby-foundations-20261101/lesson-2/lesson.html

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+<!doctype html><html lang="en"><meta charset="utf-8"><title>Values and decisions</title><h1>Values and decisions</h1><p>15-minute session: read for 3 minutes, trace for 3, experiment for 7, and complete the check for 2. Spend longer whenever you need.</p><p>A decision chooses which statements run. The policy here is “ready at 80 or higher.” Trace 85, 79, 80, and 81 before running each case. The comparison includes 80. A program that prints the right answer for 85 may still be wrong at the boundary. Add a separate check rejecting scores below 0 or above 100; rejection and needing practice mean different things.</p><p><code>puts</code> prints a line. <code>def</code> and <code>end</code> delimit a method. <code>each</code> yields values to a block. An instance variable beginning with <code>@</code> belongs to an object; two objects can hold different values.</p><pre><code class="language-ruby">score = 85
+if score &gt;= 80
+  puts &quot;Ready&quot;
+else
+  puts &quot;Practice&quot;
+end
+</code></pre><p><strong>Expected result:</strong> <code>Ready</code></p><h3>Practice and evidence</h3><p>Keep three notes: your prediction, the actual result, and why they match or differ. The completion check grades understanding; the practice task builds skill.</p><p><a href="https://www.ruby-lang.org/en/documentation/">Language reference</a></p></html>

en/ruby-foundations-20261101/lesson-2/main.rb

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+score = 85
+if score >= 80
+  puts "Ready"
+else
+  puts "Practice"
+end

en/ruby-foundations-20261101/lesson-3/lesson.html

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+<!doctype html><html lang="en"><meta charset="utf-8"><title>Functions and a clear policy</title><h1>Functions and a clear policy</h1><p>15-minute session: read for 3 minutes, trace for 3, experiment for 7, and complete the check for 2. Spend longer whenever you need.</p><p>A function or subroutine names a reusable calculation. Our policy accepts nonnegative total and completed counts and returns zero when completed reaches or exceeds total. Otherwise it returns their difference. Trace (4,1), (4,4), (4,5), and (0,0). Keep printing separate from calculation. Write down why negative inputs are outside this exercise’s domain, then design an explicit rejection policy before accepting external input.</p><p><code>puts</code> prints a line. <code>def</code> and <code>end</code> delimit a method. <code>each</code> yields values to a block. An instance variable beginning with <code>@</code> belongs to an object; two objects can hold different values.</p><pre><code class="language-ruby">def remaining(total, done)
+  [0, total - done].max
+end
+
+puts remaining(4, 1)
+</code></pre><p><strong>Expected result:</strong> <code>3</code></p><h3>Practice and evidence</h3><p>Keep three notes: your prediction, the actual result, and why they match or differ. The completion check grades understanding; the practice task builds skill.</p><p><a href="https://www.ruby-lang.org/en/documentation/">Language reference</a></p></html>

en/ruby-foundations-20261101/lesson-3/main.rb

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+def remaining(total, done)
+  [0, total - done].max
+end
+
+puts remaining(4, 1)