Solve this quadratic equation 2x^2+x-5 = 0

Could somebody me with this radical simplification?

Three numbers x, y, and z are in the ratio 2: 7: 8. if 12 is subtracted from y, then three numbers form a geometric sequence (in the order x, y–12, z). find x, y, and z. there are 2 sets.

What is the radius of a circle with an area of 78.5 cubic inches? use 3.14 for pie