Mhanifa can you please help? It says RST and HKN btw

1. what is the formula for finding the vertical distance between two points on a coordinate plane?

Acircle has a radius of 5/6 units and is centered at (3.6, 7.8) write the equation of this circle

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.