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.
