Set 5: Linear Equations

Choice C is correct. Choice B is the correct answer. This is a special case demonstrating the additive identity. 1. Start with the equation: $x + 18 = 18$ 2. Subtract 18 from both sides: $x = 18 - 18$ 3. Simplify: $x = 0$ 4. Verify: $0+ 18 = 18$ ✓ When we add zero to any number, the number remains unchanged. This is the additive identity property. Zero Matters: Never assume zero can't be a solution! It's a perfectly valid answer that appears frequently in mathematics. Choice D is incorrect because this results from adding instead of subtracting: $18+ 18 = 36$. This is the wrong operation. Choice A is incorrect because this confuses the constant (18) with the solution. Seeing 18 on both sides doesn't mean $x = 18$. Choice B is incorrect because this might come from thinking "the same numbers divide to 1," but division isn't how we solve addition equations.