Ihave to rewrite an equation so that y is a function of x. i think i'm solving for y, because on my examples it has "y=". how do i do this?

You do whatever you need to do to one side of the equation in order to have
only ' y ' left on that side, AND every time you do something to that side of
the equation, do exactly the same thing to the other side.

Here are three examples, out of the 9 answers you want handed to you:

#16:                                  3x + 5y = 7

Subtract  3x  from each side:      5y = -3x + 7

Divide each side by  5 :                y = -3/5 x + 7/5



#17:                                     13 = 12x - 2y

Add  2y  to each side:    2y + 13 = 12x

Subtract 13  from each side:  2y = 12x - 13

Divide each side by  2 :          y = 6x - 13/2



#22:                                1/4 y + 3 = -5x

Subtract  3  from each side:   1/4 y = -5x + 3

Multiply each side by  4 :            y = -20x + 12