Joanie wants to mail a package that requires $1.61 in postage. If she has only 5 cent and 8 cent stamps. what is the smallest number of stamps she could use that would total exactly $1.61?

Answer 1

number of 5 cent stamps --- x
number of 8 cents stamps ---- y

5x + 8y = 161
y = (161 - 5x)/8 , clearly 0 < x < 33
after a few tries I got
x = 5, y = 17
since the slope is -5/8, other values are:
x = 13, y = 12
x = 21 y = 7
x = 29 , y = 2

the smallest sum is 5+17 = 22