ok so find how much work each can do per hour
irst person is 5 hours to do all room
therefor
1 hour=1/5 room
2nd person takes 8 hours to do all room
therefor
1 hour=1/8 room
since working together, add times
1 hour=1/5+1/8
make denoms same
1hour=8/40+5/40=13/40
13/40 room times x hours=1 whole room
multiply both sides by 40/13 to cleaf raction (13/40 times 40/13=520/520=1)
xhours=40/13hours
xhours=3 and 1/13 hours
