It takes sarah 3 hours to edge the lawn
so her rate = 1 lawn/ 3 hours
Jesse takes 2.5 hours, so his rate = 1 lawn / 2.5 hours
Together they will take a combined rate of sarah + Jesse
= 1/3 lawn/hour + 1/2.5 lawn/hour
= 1/3 + 1/5/2
= 1/3 + (1 x 2/5)
= 1/3 + 2/5 = 11/15 lawn/hour = 1/r
r = 1/11/15 = 15/11
The time = 15/11 =1 4/11 hours
