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 help 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

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?

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18 friends, 9$ per T-Shirt, 15$ per Sweatshirt, total of 180.

If he wants to spend all his money on buying gifts, first for t-shirts.

9 * 18 = $162 total.

180 - 162 = 18, +2 extra shirts, leaving him at zero.

He'd have to buy 20 shirts.

Sweatshirt:

15 * 18 = too much money, but if you decrease 6 shirts.

15 * 12 = exactly $180, but sad how 6 friends don't get shirts.

So he can buy 12 sweatshirts.