Answer 
Tyler to do the job alone =18/1 = 18 hrs 
Solution 
It takes Tyler twice as long as Kyle to complete the same job. 
efficiency of Kyle is twice the efficiency of Tyler 
Let x be the efficiency of Tyler the efficiency of Kyle is 2x 
efficiency of Tyler : efficiency of Tyler = x :2x =1:2 
Therefore total efficiency = 1 + 2 =3x 
The total job = efficiency x total time 
Here total time to complete the job=6 hrs 
Total job =18 
Time taken to complete the job =Total job/efficiency 
Tyler to do the job alone =18/1 = 18 hrs 
Kyle to do the job alone =18/2 = 9 hrs