Question 811036
John time is 5 hours = 1/5   
Steve time is 4 hours = 1/4       
LCM is 20. (5 x 4 = 20) 

Therefore, 4/20 + 5/20= 9/20 

20/20 - 9/20 = 11/20 

x/5= 11/20

Cross Multiplying

20x=55

Therefore x = 55/20 

Time John took to complete the job is = 2.75 hrs