Set 3: Linear Equations (Intermediate)

Choice C is correct. Choice C is the correct answer. This is a classic two-step equation. We need to undo addition first, then multiplication. 1. Start with the equation: $2x + 5 = 15$ 2. Subtract 5 from both sides: $2x = 15 - 5$ 3. Simplify: $2x = 10$ 4. Divide both sides by 2: $x = \frac{10}{2}$ 5. Simplify: $x = 5$ 6. Verify: $2(5) + 5 = 10 + 5 = 15$ ✓ Order of Operations: When solving, we reverse PEMDAS. We deal with addition/subtraction before multiplication/division. Choice D is incorrect because this results from forgetting to divide by 2 after subtracting: $2x = 10$, so student thinks $x=10$. Choice B is incorrect because this results from adding 5 instead of subtracting: $15+ 5 = 20$, then $20 /2 = 10$. Or perhaps dividing 15 by 2 first. Choice B is incorrect because this results from adding 5 to 15 to get 20, and then maybe forgetting to divide.