Given:
Babysitting =$11/hours
Tutoring=$17/hours 
Total work hours is=12 hours
Minimum many earn=$150
Work 2 houre for babysitting 
so money earn is:

Earn amount is $ 22 
then required amount is:

so tutoring time for reuired amount is:

so 7.52 hours is tutoring time and 2 hours babysitting then it 9.52 hours achieved minimum earn amount 
so minimum hours for tutoring is 7.52 hours.