Set up a ratio. x/12 min = 215 ft sq/22 min. Solve for x by cross multiplying (cross multiplying is a shortcut - if you need a better explanation of cross multiplying, ask). 12 x 215 = 2580, then 2580/22 = about 117.27 ft sq. (value is actually 117.2727272727...) Answer: Approximately 117.27 ft sq can be mowed in 12 minutes.