I'm in algebra 2, so i don't remember theorem names anymore. But I think I know how to solve it. M and N are parallel, which means that the angles that form are equal to each other on opposite sides. We also know that a flat line adds up to 180 degrees. 6x+7 + 4x-7 add up to 180. (They are not equal angles) Solve for x. 10x=180 x=18.
Now for the y value. 6x+7 and 3y-20 are equal to each other, because they are opposite angles. 6(18)+7=115. set y equal to 115. 3y-20=115. 3y=135