Basically the question is asking YOU when you hear “system of equations” what do you think about it - what do you already know about system of equations. Basically. Btw enjoy this picture.
Assuming we have parallel lines, we can solve for x. Since a = 3x - 10 (vertically opposite angles are equal), 3x - 10 = 2x + 15 (alternate angles are equal) x = 25