kai spent 13.60 dollars on 20 stamps. There are only 50-cent-stamps and 30-cent-stamps. How many of each

Answer 1

x + y = 20 so y = 20 - x

50 x + 30 y = 1360

50 x + 30 (20-x) = 1360
50 x + 600 - 30 x = 1360
20 x = 760
x = 76/2
etc