20l+25g−1020, l, plus, 25, g, minus, 10

Solve for x i'll try to attach the files bc it's not letting me for some reason

The fence around a quadrilateral-shaped pasture is 3a^2+15a+9 long. three sides of the fence have the following lengths: 5a, 10a-2, a^2-7. what is the length of the fourth side of the fence?

The circle below is centered at the point (3, 1) and has a radius of length 2. what is the equation?