Answer:
The time taken by both when they work together is 2 hours 42 minutes . 
Explanation:
Given as :
The time taken by Ryan to dig 10 ft by 10 ft hole = x = 5 hours
The time taken bu Castel to dig 10 ft by 10 ft hole = y = 6 hours
Let The time taken by both when they work together = z hours
According to question
 The time taken by both when they work together = time taken by Ryan to dig 10 ft by 10 ft hole + time taken bu Castel to dig 10 ft by 10 ft hole 
i.e 
 =
 = 
 +
 + 

Or, 
 =
 = 
 +
 + 
 
 
Taking LCM
 Or, 
 =
 = 

Or, 
 =
 = 

Or, z = 
 hours
 hours
∴ z = 2 hours 42 minutes
So, The time taken by both when they work together = z = 2 hours 42 min
Hence, The time taken by both when they work together is 2 hours 42 minutes . Answer