Answer:
16 hours
Step-by-step explanation:
Let the mechanic works for x hours to make a money of $350.
Fixed charges = $30
Charges per hour = $20
So, charges for x hours = $20x
Total money earned = $350
![\implies \: 20x + 30 = 350 \\ \\ \implies \: 20x = 350 - 30 \\ \\ \implies \: 20x = 320 \\ \\ \implies \: x = (320)/(20) \\ \\ \implies \: x = 16 \: hours](https://img.qammunity.org/2023/formulas/mathematics/college/hdzpiebja25rnm0to01orhil8j2lqbq0td.png)
Thus, the mechanic needs to work for 16 hours to make $350.