jay can paint 1 house in 5 hours
jay can paint 1/5 house in 1 hour
david can paint 1 house in 3 hours
david can paint 1/3 house in 1 hour
ok, so
in 1 hour, they can paint 1/5+1/3 house
1/5+1/3=3/15+5/15=8/15 house
so
8/15 house per hour times x hours=1 house
times both sides by 15/8
x=15/8 hours
x=1 and 7/8 hour
it will take 1 and 7/8 hour or 1.875 hour or 1 hour and 52.5mins