Given: If X, then not Y. If not Y, then Z. Y is true. So:

step-by-step explanation:

for volume, add base x height x width

given the equation is 8+9z=-6, the first step would be to subtract the 8 from both sides:

8+9z-8=-6-8

since 8 minus 8 = 0, this would cancel out the 8. and since -6 minus 8 equals -14, the equation would look like this

9z = -14