Question 708632
r for rate
t for time in minutes
1 job is "shoveling the snow off the driveway".


Shoveler___________rate_________time____________jobs
Bertha______________r
Gertrude__________1/40
Both______________1/30


Usually one would try to fill in this whole table, but seeing enough information for expressions for rates, and knowing that their rates are additive, we have enough as shown.

{{{r+1/40=1/30}}}, find r, Bertha's rate.