How many brick would you need if the area is 320 square feet and one brick is 4x8?

The question does not specify the units used for the size of each brick. Assuming the brick's dimensions are given in inches, each brick covers 4" x 8" = 1/3 ft x 2/3 ft = 2/9 sq ft.

Area to be covered = 320 sq ft so minimum number of bricks required = 320 / (2/9)

= 1440 bricks.

That answer assumes that the area to be covered is well behaved and that all offcuts are used.