Solution: Find the relationship between the coach class seat and the first class seat. Then solve for the unknown.
First class seat = x
Coach class seat = 6x + 5
x + 6x + 5 = 152
7x = 147
x = 21 <======== number of first class seats
6x + 5 = 6 x 21 + 5 = 131 <======== number of coach class seats
