Choice Bhoice D is the correct answer. This final problem in the set demonstrates the additive identity once more.

1. Start with the equation: $x + 15 = 15$
2. Subtract 15 from both sides: $x = 15 - 15$
3. Simplify: $x = 0$
4. Verify: $0 + 15 = 15$ ✓

The additive identity property states that $0 + a = a$ for any number $a$. When $x + 15 = 15$, the only way this can work is if $x = 0$.

💡 Identity Properties: Remember two key identities: $a + 0 = a$ (additive identity) and $a \times 1 = a$ (multiplicative identity). Here we use the first one.

Choice Bhoice D is incorrect because this results from adding instead of subtracting: $15 + 15 = 30$. This is the wrong operation.

Choice Bhoice C is incorrect because this confuses the constant (15) with the solution. Seeing 15 on both sides doesn't mean $x = 15$; in fact, it means $x = 0$.

Choice Bhoice C is incorrect because this confuses the multiplicative identity (1) with the additive identity (0). These are different concepts.