Question 104831
let s=streamers, p=hats


Three rolls of streamers and 15 party hats cost $30 ... 3s+15p=30 ... s+5p=10 ... s=10-5p


you bought 2 rolls of streamers and 4 party hats for $11 ... 2s+4p=11


substituting from first equation to second ... 2(10-5p)+4p=11 ... 20-10p+4p=11 ... -6p=-9


solve for p and substitute back to find s