#10 &11 test corrections! Help pls

#10:
Let's first find thr volume of te fish tank. The formula is LWH. (12×12×24). The product is 3,456. Since we need to find the volume of the gravel we have to find the percent increase of 85% to 95%. That is 10%. So now, all we have to do is find 10% of 3,456, which is 345.6. The answer is (C) 345.6

#11:
Because the volume of Box B is TWICE of the volume of Box A, we need to find out what half of Box B's volume. Again, the volume formula is LWH. (8×12×20). The product is 1,920. Divide that by 2, and the quotient is 960. Now we know that (6×10×the height) should equal 960. We will substitute x for the height, and it becomes (6×10×x=960). I'm pretty sure you know how to evaluate this expression, but just in case, here it is:
6×10×x=960
60x=960
60x/60=960/60
x=16

The height for Box A is 16.

Hope this helps!!!