Problem:

kenny wants to by gifts for all 18 friends. he can buy t-shirts for $9 and sweatshirts for $15. he has a total of $180 to spend. if he wants to spend all of his money, how much of each gift can he buy?



let t = # of t-shirts bought
let s = # of sweatshirts bought

the two equations for this problem are:

150 = 9t + 15s & t + s = 18

what i need with:

i can't figure out how to solve it. other problems that are similar typically have a (t = s - 18) or something so you can insert it into the bigger equation and solve. i have tried subtracting both the t and s and neither of them come up with the correct answer (i have the answers already, but no clues as to how to solve it).

if you can figure out how i can solve it from here, it'd be most appreciative.

- kat