Suppose you bought supplies. three rolls of streamers and 15 party hats cost $30. later, you bought 2 rolls of streamers ad 4 party hats for $11. solve a system of equations to determine the cost of streamers and party hats, find their costs.

Since 30÷15 is 2 you now know each party hat is 2 dollars. Now we know that and we can easily find out how much a roll of streamer is. 11-(4x2)=3. 3÷2=1.5. One roll of streamer is $1.50 and one party hat is $2. I'm pretty sure I did this right lol I hope it helps