Question 959398
1/60+1/X=1/15
1/X=1/15-1/60
1/X=4/60-1/60
1/X=3/60
3X=60
X=60/3
X=20 HOURS FOR THE NEW SWEEPER TO IT ALONE.
PROOF:
1/60+1/20=1/15
1/60+3/60=1/15
4/60=1/15 CROSS MULTIPLY.
60=60