Set 1: Linear Equations (Advanced)

Choice A is correct. Choice A is the correct answer. When solving $x - a = b$, we add $a$ to both sides. 1. Start with the equation: $x - 18 = 5$ 2. Add 18 to both sides: $x = 5 + 18$ 3. Calculate: $x = 23$ 4. Verify: $23- 18 = 5$ ✓ The key is recognizing that addition is the inverse operation of subtraction. Choice C is incorrect because this results from subtracting 18 from 5: $5- 18 = -13$. This applies subtraction twice instead of using the inverse operation (addition). Choice D is incorrect because this is the absolute value of Choice C. Some students might calculate $5- 18 = -13$ and then drop the negative sign, giving 13. Choice C is incorrect because this is the negative of the correct answer. If you mistakenly subtract instead of add and then apply a negative: $-(5 + 18) = -23$.