Let us say there are total x number of stamps.
Number of stamps from Mexico are 18.
Fraction of stamp from Mexico = 3/8 of total stamps.
Equation for this would be:
[tex] \frac{3}{8} x =18 [/tex]
dividing right side by 3/8,
x = 18÷ 3/8
x = 48
So total number of stamps are 48.
We have to find number of stamps from United States.
Stamps from United states = total stamps - stamps from Mexico = 48 -18=30
Stamps from United states are 30.