15) n-4-9
16) 4n-n
17) –3x – 9+15x
18) -9k + 8k
19) -16n - 14n
20) 15n - 19n
21) -4 +7(1 – 3m)
22) –5n+ 3(6 + 7n)

Jabari is power washing houses for a summer job. for every job, he charges an initial fee plus $30 for each hour of work. his total fee for a 4 -hour job, for instance, is $170 . jabari's total fee,f, for a single job is a function of the number,t, of hours it takes him to complete the job. write the function's formula.