How do I know where to plug in the center and the diameter in a circle equation

If the dimensions of a rectangular prism are 5 ft x 3.5 ft x 2 ſt, what is the surface area?

Find the zeros of each function. f(x) = x^2 + 5x - 6

Abicycle training wheel has a radius of 3 inches. the bicycle wheel has a radius of 10 inches.approximately how much smaller, in square inches and rounded to the nearest hundredth, is the area of the training wheel than the area of the regular wheel? *