If the nth term of an ap is 7-4n .find its common difference

Find the missing dimension extra points

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? *

The value of the expression 16-^3/4 8 1/8 -6 6 1/40 1/64