Sandy rakes and bags the leaves on her front lawn in 30 minutes. Randy does the same job in 20 minutes. How many fewer minutes will it take to complete the same job if Sandy and Randy work together than if Sandy works alone?
Randy rate 1 job 20 minutes = 1/20
Sandy = 1/30
1/30 + 1/20 = 1/x x is the minutes for both of them to complete the job
solve for 'x' then you answer is sandy time - x = 30 - x