Question 313764
let us assume shovelling the driveway as 1 job.
Janet can do it in 65 minutes.
so she can do 1/65 of the job in 1 minute.
..
Tom can do the same job in 50 minutes.
So he can do 1/50 of the job in 1 minutes.
..
Both together will do 1/50+1/65 of the job in 1 minute. LCM =650
65+50 / 3250 
115 /3250 of job they do in 1 minute.
so they together can do the job in 3250 / 115 minutes
= 28.2 minutes