How many 12X18 inch pavers do I need to cover 120 square feet?

Convert the inches to feet

Hence

12 inches = 1 ft

18 inches = 1.5 feet.

Multiply together to bring to sq.ft.

Hence 1 ft X 1.5 ft. = 1.5 sq.ft.

Divide

120 sq.ft. / 1.5 sq.ft.

Hence

= 80 paveing stones/flags. required.