#1 There is no area of a cube. There is only a volume.
#2 The formula is

where s is the side.
Substitute 729 in V since that is the volume.

Take the cube root and you will get
9.
So the formula is
and the side is 9.
4.95+4.95×0.05=5.20
5 dollars 20 cents
Only Table 2 shows direct variation. Every y value is 7 times the associated x value.
X=3
Just look at where the two lines intercept and see the x value