Jack was planting a tree. He was to dig a hole that was 3 feet deep for every 5 feet of tree height. How deep should he dig the hole for a tree that is 17feet high.
Calculations
Cross multiplication

=
5x = 2 x 13
Divide by 5 to isolate x

=
x = 10.2
Answer = 10.2
2x+3 + 3x-4 + 2x+3 + 3x-4 = 78
10x -2 = 78
10x = 80
x=8
deck is 2(8)+3 by 3(8)-4, or 19 by 20