Question 286537
$9x+$15y=$189
x+y=15 or x=15-y
Now replace x with (15-y) in the first equation & solve for y.
9(15-y)+15y=189
135-9y+15y=189
6y=189-135
6y=54
y=54/6
y=9 $9 dollar pizzas were bought.
x=15-9=6 $15 dollar pizzas were bought.
Proof:
9*15+6*9=189
135+54=189
189=189