Answer:
4
Step-by-step explanation:
The total amount was $120.
A portion of the $120 was for parts.
The rest of the $120 was for service. Service cost $12 per hour.
Start with $120.
Subtract $72 to find the amount spent on service.
$120 - $72 = $48
$48 was spent on service.
The service costs $12 per hour.
$48/($12/hour) = 4 hours
Answer: 4 hours
Check:
$72 in parts + 4 hours * $12/hour = $72 + $48 = $120
4 hours is correct.
