Answer:
d) subtract 15 from both sides
Explanation:
Process of elimination:
a) 2.5 and x are being multiplied, not subtracted, so (a) is wrong right off the bat.
b) you may divide 2.5 by both sides, but you want to get "x" on one side first. So you would do (b) first either.
c) to get rid of 15, which we need to somehow, we need to do the opposite operation than the one in the equation. 15 is +15, not negative, and so you would need to subtract to get rid of 15. This is why (c) is also wrong.
That leaves us, with (d), because you need to subtract 15 to isolate "x".