I’m not 100% sure but I believe it’s A
Answer:

Step-by-step explanation:
Let
x-----> the number of girls
y-----> the number of boys
we know that
-----> equation A

isolate the variable y
-----> equation B
Substitute equation B in equation A



You make an x= ... equation by moving 2y to the other side and /3 (in the first equation) then you fill in x into the second equation and you calculate y. If you have Y you fill it in in the first equation.
The second choice, 8 and 9 since they’re the numbers being multiplied by a variable.