Does this graph represent a function why or why not

Ahigh definition tv cost $800 with a down payment of 2/5 of the cost. how much is left to pay, in dollars after the down payment has been made?

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.

Prove that 16^4-2^13-4^5 is divisible by 11.