Algebra
posted by Bob .
How do I set this up to solve?
In 2004, the Diabetic Express charged $27.06 for a vial of Humulin insulin and $34.39 for a vial of Nevolin Velosulin insulin. If a total of $1565.57 was collected for 50 vials of Insulin, how many vials of each type were sold?

Solve this pair of equations for x and y.
x + y = 50
27.06 x + 34.39 y = 1565.57
Try substiting 50x for y in the second equation.