how long to mow the lawn

Question

twin brothers, billy and bobby, can mow their lawn together in 97 minutes. billy could mow the lawn by himself in 20 minutes less time that it would take bobby. how long would it take bobby to mow the lawn by himself?

Answer 1

Bobby's time to mow the lawn is x

 

Billy's time to mow the lawn is x - 20

 

Billy and Bobby together is 97

 

solve for x:

 

x + x-20 = 97

 

2x = 97 + 20

 

2x = 117

 

x = 58.5 minutes for Bobby to mow the lawn.