Janice bought 5 bags of gummy bears at $0.85 each and 9 packs of gum at $1.20 each for her class party.

express what she purchased mathematically.

5 times 0.85 = 4.25 gummy bears
 9 times 1.20 = 10.80 gum
10.80 + 4.25 = 15.05 total

4.25 + 10.80= 15.05

5 x 0.85 = 4.25

9 x 1.20 = 10.80

First, find out how Aaron earned from the hours he worked plus the commission(c):
6.75 x 17 + c = 290.63
114.75 + c =290.63
Now we can work out c:
c = 290.63 - 114.75 = 175.88.
Aaron's commission is calculated as a percentage(p) of sales:
3350 x p/100 = 175.88
Multiply both sides by 100:
3350 x p = 17588
Now we can calculate p by dividing both sides by 3350:
p = 17588/3350 = 5.25%