Answer:
$3x+$5y=C and the total cost is $ 78
Explanation:
the equation first is going to be $3x+$5y=C
x: small balloons
y: large balloons
c: total cost
Now to find the how much the total cost is, you should substitute the variables and then solve the equation.
x: 11
y:9
3(11)+5(9)= 33+45
78