Ok the answer is 4 hours because...
our total is 217 and we know that without the hours 97 + something = 217 so we subtract 97 from 217 (217-97) and we get 120. Then we know that 30 x the number of hours = 120. Therefore to find the number of hours we divide 120 by 30 (120/30) which gives us 4. When we plug everything back in, 30 x 4(# of hours) + 97 = 217