Question 142242
7*x/(7+x)=3
7x=3(7+x)
7x=21+3x
7x-3x=21
4x=21
x=21/4
x=5.25 hours for the mom cleaning the room alone.
Proof:
7*5.25/(7+5.25)=3
36.75/12.25=3
3=3