Question

If i have 8 foot piece of wood to trim bookshelf, I need 100 inches lumber for trim, do i have enough lumber?

Answer 1

There are 12 inches in a foot.  If you have an 8 foot piece of wood you have to multiple that by 12 inches.  8 x 12 is 96 inches.  If you need 100 inches you are short by 4 inches. 

Answer 2

so first convert feet to inches
12 inches in 1 foot
8 feet
12 times 8=96
96 is less than 100
you don't have enough