On an airplane there are 2 seats on the left side in each row and 3 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 of the plane?

Every row is the same with 2 seats on the left and 3 seats on the right.
That means that what is true of one row is true of all rows combined.

In one row there are 5 seat (2 + 3 = 5).
There are 2 seats on the left, so the seat on the left are 2/5 of the seats.
The 3 seats on the right are 3/5 of the seats.

(a) Left side:

2/5 * 150 = 60

There are 60 seats on the left side.

(b) Right side:

3/5 * 150 = 90

There are 90 seats on the right side.