Substitute into second equation: \(4(3) - y = 10\) → \(12 - y = 10\) → \(y = 2\).

["How to Substitute into the Second Equation: Solving (4(3) - y = 10 \‌ (12 - y = 10 \‌ y = 2)", "Solving equations through substitution is a powerful algebra technique that simplifies complex problems into manageable steps. In this article, we’ll explore how substituting values into a second equation helps solve equations like (4(3) - y = 10 \‐ (12 - y) = 10) and correctly derives the solution (y = 2).", "### Understanding the First Equation: (4(3) - y = 10)", "Before substitution, simplify the left-hand side of the equation:", "[\n4(3) - y = 10 \Rightarrow 12 - y = 10\n]", "This gives us:", "[\n12 - y = 10\n]", "Rearranging lets us isolate (y):", "[\n-y = 10 - 12 \Rightarrow -y = -2 \Rightarrow y = 2\n]", "So, the direct solution to (12 - y = 10) is (y = 2). But substitution becomes crucial in more complex equations where values replace variables to maintain clarity.", "### Substituting into a Related Equation", "Consider a system or connected pair of equations such as:\n[\n12 - y = 10 \quad \ ext{and} \quad 12 - y \‐ (y - 2) = 0\n]\n(Note: The original problem statement hints substitution involvement, though the equations appear linear. Substitution strengthens understanding.)", "To substitute (y = 2) into the second equation, plug (y) directly:", "[\n12 - y \‐ (y - 2) \Rightarrow 12 - 2 \‐ (2 - 2) \Rightarrow 10 \‐ 0 = 10\n]", "This confirms the substitution is valid and maintains equality, supporting the solution.", "### Why Substitution Helps: Key Benefits", "- Clarity: Separating expressions into substitutable parts reduces complexity.\n- Verification: Substituting solved values validates the solution in real-world equations.\n- Extensibility: Substitution enables solving systems beyond single linear equations.", "### Practical Example: Linear Equation with Substitution", "Suppose you have:", "[\nx = 3, \quad 4x - y = 10\n]", "Substitute (x = 3) into the second equation:", "[\n4(3) - y = 10 \Rightarrow 12 - y = 10 \Rightarrow y = 2\n]", "Here, substituting the value of (x) into one equation helps solve for (y) efficiently.", "### Final Thoughts", "Substitute into second equations—whether literal or part of a system—to simplify and verify solutions algebraically. In the example (12 - y = 10 \‐ (12 - y) = 10), substitution confirms (y = 2) maintains equation balance, making it a solid teaching and solving strategy.", "Keywords: substitute into equation, solve (4(3) - y = 10), substitution method algebra, solving linear equations, verify solution with substitution, step-by-step algebra.", "---", "Mastering substitution strengthens algebraic fluency—use it to unravel complex equations with confidence."]