On an airplane there are two seats on the left side in each row and three seats on the right side. there are 150 seats altogether.
a. how many seats are on the left side of the plane?
b. how many seats are on the right side?

In order to solve these you first need a ratio.
From what we can tell, the ration from LEFT to RIGHT is:
2:3
Therefore, in order to have a 2:3 ratio, we need 5 parts total (2 parts on left + 3 parts on right = 5 total parts!) 

A) 60

B) 90