Angle A is (2y-5) and Angle D is (x+50). The exterior angle of Angle C is (3x+20). What is x and y?

I am pretty confused with this one. I know that the opposite angles of a parallelogram equal each other, so Angle C is (2y-5). Angle C+the exterior angle of it=180, right? I tried doing this:

(2y-5)+(3x+20)=180

I plugged in (180-x) into y when I wanted to solve for x.

[2(180-x)-5]+(3x+20)=180

360-2x-5+3x+20=180

375+x=180

x=-195

I don't know how I ended up with a negative x value, and I know this won't work for the parallelogram angle. I think I did something wrong when I replaced the y with 180-x.