X + y = -15. Subtract x from both sides.
y = -x - 15. This is as far as we can go with the provided information.
-5.8 + (-2.5) = -8.3
since both the number are negative you simply add the numbers and use the negative sign.
I am learning this right now but in two hours I will tell you
2 61/64m^3; For a rectangular prism, just use the formula V=w h l
V=0.875*1.5*2.25
V=1.3125*2.25
V=2.953125
V=2 61/64m^3