WHEN adding integers and the signs are different, how do you know what the sign will be?

Step-by-step explanation:

when you add integers remember that the positive integers move you to the right (so the integer will increase) and negative integers move you to the left (so the integer will decrease)

Hope this helps.

y - 25 = 2 ( x - 10 ) should be the answer

well in order to answer the question, you have to give us the dimensions of the prism first.