That is the answer..............
It is good equation. Look, that:
81 = 3 x 3 x 3 x 3 = 3^4.
So you have to solve:
3^x = 3^4
exponents have to be the same, so
x=4
That's mean that A(4) = 81
A rectangle, presumably, as the cross section is going to be whatever shape the outward faces are (in the case of a vertical cross section like this one)
First you'll have to bring the equation in form y = mx + b.
4y = -x - 32
y = -1/4 x - 8
So the slope is -1/4 and y-intercept is -8
Hope this helps :)