Set 10: Linear Equations

Choice D is correct. Choice D is the correct answer. We add to undo subtraction, then divide. 1. Start with the equation: $4x - 8 = 12$ 2. Add 8 to both sides: $4x = 12 + 8$ 3. Simplify: $4x = 20$ 4. Divide both sides by 4: $x = \frac{20}{4}$ 5. Simplify: $x = 5$ 6. Verify: $4(5) - 8 = 20 - 8 = 12$ ✓ Choice A is incorrect because this results from subtracting 8 from 12: $12- 8 = 4$, then $4 /4 = 1$. We must add to undo subtraction. Choice C is incorrect because this is the value of $4x$. The variable is not yet isolated. Choice B is incorrect because this results from multiplying 20 by 4: $20\times 4 = 80$. We need to divide.