A 16-foot board is to be cut into two pieces so that one piece is 4 feet longer than the other. How long will the longer piece be?

10 feet

Step-by-step explanation:

If x is the length of the longer piece, and y is the length of the shorter piece, then:

x + y = 16

x = y + 4

Substitute:

x + (x - 4) = 16

2x - 4 = 16

2x = 20

x = 10

The longer piece will be 10 feet long.