The plane PRS passes through the points P, R and S. So it contains the line RS. Also the plane QRS passes through the points Q, R and S. So it contains the line RS as well. Since both the planes contain the line RS, the line RS must be the intersection of plane PRS and QRS
If they're equal set them equal to each other if they're supplementary you set up an equation. Where you add them up and set them equal to 180. And then you just want to solve for X.
an infinite number of triangles can be formed if the judgement is on 2 angles but with 1 side length, the whole triangle needs to relate to the side of that side.
