SOLUTION: Ben was in charge of ordering 35 pizzas for the office party. He ordered three types of pizza: cheese, pepperoni and supreme. The cheese cost $9, pepperoni $12 and supreme $15. He

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Question 962934: Ben was in charge of ordering 35 pizzas for the office party. He ordered three types of pizza: cheese, pepperoni and supreme. The cheese cost $9, pepperoni $12 and supreme $15. He spent exactly twice as much on the pepperoni as he did on the cheese pizzas. If been spent a total of $420, how many pizzas of each type did he buy?
x+y+z=35
9x+12y+15z=420
x=? y=? z=?

Answer by Fombitz(32388) About Me  (Show Source):
You can put this solution on YOUR website!
1.x%2By%2Bz=35
.
.
.
P=2C
12y=2%289x%29%7D%7D%0D%0A%7B%7B%7B12y=18x
2.2y=3x
.
.
.
9x%2B12y%2B15z=420
3.3x%2B4y%2B5x=140
Multiplying eq. 1 by 5 and subtracting from eq. 3,
3x%2B4y%2B5z-5x-5y-5z=140-175
-2x-y=-35
Multiply by 3.
-6x-3y=-105
Substitute from eq. 2,
-2%282y%29-3y=-105
-4y-3y=-105
-7y=-105
y=15
Then,
2%2815%29=3x
x=10
And,
10%2B15%2Bz=35
z=10