(6 ft)(3 ft) = 6*3 ft

I find it helpful to keep the units with the numbers. That way you don't end up with a meaningless number at the end of your calculation. The units multiply and divide just like variables do.

^{2}= 18 ft^{2}18 ft^{2}= (18 ft^{2})*(12 in/ft)^{2}= 18*144 in^{2}= 2592 in^{2}I find it helpful to keep the units with the numbers. That way you don't end up with a meaningless number at the end of your calculation. The units multiply and divide just like variables do.