Mr. sharrone can paper a room in 3 hours. his assistant needs 5 hours. if mr. sharrone works 1 hour and then his assistant completes the job alone, how long will it take the assistant to finish the job?

Mr Sharrone can do 1/3 of the job each hour 
the assistant does 1/5 of the job each hour 

1(1/3) + H (1/5) = 1 (complete job) 
1/3 + 1/5 H = 1 
1/5 H = 1 - 1/3 = 2/3 
H = (2/3) / (1/5) = 10/3 = 3 1/3 hours to complete the job

Ithink it's the first one ( let me know if it right)