In: Advanced Math
Karon went to the post office and spent $31.57 on 84 stamps. She bought 27¢ stamps for all the postcards, 42¢ stamps for each letter addressed to friends in the U.S., and 94¢ stamps for each letter to England. Karon bought 7 times as many postcard stamps as those for the letters to England. How many postcard stamps did Karon buy? (Hint: Use matrices.)