How do i do this i'm am really confused?

Since (4y-42) and 2y are opposite angles, they equal to each other which looks like this:

4y-42 = 2y

From there you want to put the y onto one side:

4y-2y-42=0  >   2y-42=0

You want to balance the equation out and move the -42 onto the other side so you add it to both sides to get:

2y=42

Then divide both sides by 2 to get:

y= 21

From there you can plug 21 back into the original equation to find each angle.

4(21)-42 = 2(21)    --->   84-42 = 42  ---> 42 = 42

So y = 21 and each angle is 42 degrees

C. i possibility the answer to this