A plumber charges $30 an hour plus cost of parts. The parts to fix Ben’s sink cost $97. The plumber gives Ben a bill for $217. How long did it take the plumber to fix Ben’s sink?

X is hours

30x + 97 = 217
30x + 97 - 97 = 217 -97
30x = 120
30x/30 = 120/30
x = 4

They took four hours to fix Ben’s sink.

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