Answer:
Let G represents the green seats and B represents the Blue seats.
As per the statement:
There are three blue seats for every two green seats in the cafeteria.
⇒ for every two green seats, there are three blue seats.
then;
For every 1 green seats, there are 3/2 blue seats
i.e,
.....[1]
It is also given that if there are 80 total seats in the cafeteria.
then;
.....[2]
Substitute the equation [1] into [2] we get;

Combine like terms;

Multiply by 2/5 both sides we get;

Therefore, there are 32 blue seats.