Let n be the number of the $9 pizzas.
Then the number of the $7 pizzas is (30-n).
Write the total money equation
9n + 7(30-x) = 250 dollars.
Simplify and find n
9n + 210 - 7n = 250
9n - 7n = 250 - 210
2n = 40
n = 40/2 = 20.
ANSWER. 20 pizzas at $9 each and 30-20 = 10 pizzas at $7 each.
CHECK. 20*9 + 10*7 = 180 + 70 = 250 dollars total. ! correct !
PRICES QUANTITY COST
7 30-d 7(30-d)
9 d 9d
TOTAL 30 250
d, how many deluxe pizzas
.