Question 161166
If Jim paid $33.90 for 120 stamps, then he paid 0.2825 for 1 stamp

Using the method of alligation,

0.2825-0.23=0.0525

0.37-0.2825=0.0875

Then P/F=0.0875/0.0525

E.g. for every 0.14 stamps, 0.0875 are postcard stamps

Then for 120 stamps, P=(0.0875/0.14)(120)=75 (Answer)

First class stamps=120-75=45 (Answer)