joe and james are selling pies for a school fundraiser. Customers can buy blueberry pies and blackberry pies. Joe sold 5 blueberry pies and 10 blackberry for a total of $135. James sold 1 blueberry pie and 9 blackberry pies and 10 blackberry pies for a total of 104. Find the cost each of one blueberry pie and one blackberry pie.

This is a system of equations problem.

Blueberry = X, blackberry = Y

Joe:
5x + 10y = 135

James:
x + 9y = 104

Let’s isolate x from James’ equation.
x = 104 - 9y

Now substitute that into the first equation.
5(104 - 9y) + 10y = 135

520 - 45y + 10y = 135

-35y = -385

y = -385/-35. The negatives cancel out, leaving us with $11 for blackberries.

Now we can substitute that value into James’s equation.

x + 9(11) = 104

x = 104 - 99

x = $5

Final Blueberry pies cost $5, blackberry pies cost $11.