Question 53098
Let the number of 37 cent stamps=x
Let the rest of the 20 stamps be the 20 cent stamps=20-x
The cost of 37 cent stamps =.37x
The cost of 20 cent stamps=.20(20-x)
The total cost =7.06
.37x+.20(20-x)=7.06
100(.37x+.20(20-x))=100(7.06)
37x+20(20-x)=706
37x+400-20x=706

17x+400=706
17x+400-400=706-400
17x=306
17x/17=306/17
x=18
Allen bought 18 37 cent stamps!  (They didn't ask this time, but that means he only bought 2 20 cent stamps.)