the limit of time is 2 hours, and the time is the sum of the time spent driving: 10 minutes, and the time doing assignments.
Time doing assignments:
To find this time we multiply 18 (the average time it takes to do an assignment) by "x" which will represent the number of assignments.
So the total time Bill takes to do that is
and since the limit of time is 2 hours, but we need to represent this 2 hours in minutes (because the other two quantities are also in minutes)
2 hours = 120 minutes.
So 18x+10 must be less than or equal to 120: