Ok, so:
if we solve this expression:
1/2(3 1/2 + 0.5) - 3,
We know that (3 1/2) is equal to 7/2, which is 3.5,
So, the result of that operation will be 1/2 (4) - 3, which is equal to -1.
Then, we have to do all the operations below, and if one of more of them is equal to -1, then, both expressions are equivalent with the first one.
Let's start with A.
A. 1/2(4) -3 is equal to -1, so this expression is equivalent.
B. 4 - 1/2(3) IS NOT equal to -1, so this can't be a correct answer.
C. 3-1/2(4) is equal to 3 - 2 and this is 1, which IS NOT equal to -1, so this can't be a correct answer.
D. -3 + 1/2(4) is equal to -3 + 2, and this is equal to -1, so this expression is equivalent.
Finally, A and D are equivalent expressions.