Please help how do you do this

Arectangle plot measure 20ft. by 30ft. a 3-ft.-wide sidewalk surrounds it. find the area of the sidewalk.

Real gross domestic product: a) will increase if the price level increases. b) can change from one year to the next even if there is no change in output. c) will increase if the level of output increases. d) is a measure of inflation.

The best method for solving quadratic written in vertex form is