Kathleen made 35 pies. There were 10 slices in each strawberry pie and 7 slices in each blackberry pie. If Kathleen made 290 slices of pie in total, how many of each type of pie did she make?
Let x = number of strawberry pie, and y = number of blackberry pie
Then x + y =35 for total pies,
and 10x + 7y = 290 for total slices
Solve two equation for x and y
by substitution of y = 35 - x from the first equation
into the second, and solve for x,
x = 15, and get y = 20
therefore, 15 strawberry pies, and 20 blackberry pies.