Quick Answer: 7 dollars each
Comment
The key word is of. It means multiply. So the equation is set us as
20% of 175 =
20/100 * 175 =
0.2 * 175 = 35
So each of them will contribute 1/5 of that amount.
Tip
Tip = 1/5 * 35
Tip = 0.2 * 35
Tip = 7 dollars each.