McKenzie and lindy work on a landscaping crew

Question

McKenzie and Lindy work on a landscaping crew. They can complete the landscaping job in 2 hours if they work together. McKenzie generally takes 3 hours less Lindy. How long would it take McKenzie to complete the landscaping job if Lindy calls in sick? 

Answer 1

1/m +1/(m+3) =1/2

2m+6 +2m=m^2 +3m

m^2 -m -6 = 0

(m-3)(m+2)= 0

Mckenzie= 3 hours by himself, Lindy=6 hours by himself