Lisa can shovel snow from her driveway in 60 minutes. jim can do the same job in 35 minutes. how long would it take lisa and jim to shovel the driveway if they worked together?

60+35=95 working together in the driveway. 

The answer would be about 22.1 minutes. The reason for this is because Lisa can shovel 1/60 of the driveway in 1 minute. Jim can shovel 1/35 of it in one minute. If you add that up, 1/60 + 1/35 and by using common denominators you'd get 7/420 + 12/420 which is 19/420. If you flip that, 420/19 is about 22.1.

The original ratio is 5:7 then 2 boys join and 1 girl as well making the new ratio 4:5