You mean, what is this number?
we can rephrase it like this: the sum of a number x and 8 is 15
which is:
x+8=15
we subtract 8 from both sides and we get
x=7
so the answer is 7.
2(x + y) or 2y+x or 2x(x + y)
Hey!
You have to divide the total amount she has by the surface area.
Surface area = 2(wl+hl+hw)
That gives you:

The surface area is 126 ft. Now divide the total amount she has by the surface area.

<em>That means she can cover 9 boxes</em>

B, because the mid segment is half the length of the third side