A business executive bought 40 stamps for $13.68. The purchase included 37 cents stamps and 23 cents stamps. How many of each type of stamp were bought?

Answer 1

x + y = 40 (number of stamps)
23 x + 37 y = 1368 (number of cents)

Solve for x and y

23 (40 -y) + 37 y = 1368

Now you only have to solve for y