In a problem like this, we would need to solve for a proportion. But of coarse, we need to set one up.
8/9 gallons of paint for 4 birdhouses.
8/9/4 = x/1
8/9 *1 = 4*x
8/9 = 4x
Divide 4 by both sides.
8/9 ÷ 4 = 4x/4
x = 8/9 ÷ 4
x= 0.22 repeating
Our answer is that for each birdhouse, he use about 0.22 gallons of paint.