Which is an equation of a direct proportion? y=8x, y=12x+4, y=12x, y=4x−4

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.

Can someone me with this? i’m not sure what to put for my equations.

What is solution for the following system of equations, 2x+8y=4 and x=-3y+5 1) x=14 y=-3 2) x=2 y=-3 3) x=-3 y=-3 4)x=12 y=5