Robert sells 3 packages of cookie dough and 8 packages of pie dough for $35. Phil sells 6 packages of cookie dough and 6 packages of pie dough for $45. How much does each type of dough cost?

1 Answer
May 21, 2017

Answer:

Cookie dough: #$5#
Pie dough: #$2.5#

Explanation:

Just for shorting will call the cookie dough #(x)# and the pie dough #(y)#.

We know Robert sold #3x+8y# for 35, and Phil sold #6x+6y# for 45.
To try to get to how much each cost, we need to put aside one of 'dough'; we do so by making one of the doughs even and then eliminate it (for now)

#(3x+8y=35)" "xx(-2)#

And if we put them together and subtract one by one,

#-6x-16y=-70#

#6x+6y=45#

We get

#(-10y=-25) " ":(-10)#

#y=2.5#

Now we can return to the dough we left aside. And this time we already know how much pie dough cost so we put this, in case of Phil #6xx2.5=15#

And we left with this

#(6x+15=45) -15#

#(6x=30)" " :6#

#x=5#