Answer:
It will take luis 18 hours
Step-by-step explanation:
1/a + 1/b = 1 /t
where a is the time for one individual working alone
b is the time the second individual working alone
t is the time the two individuals working together
let a = time for tran to work
b = time for luis to work
1/9 + 1/b =1/6
multiply by 36b to clear the fractions
36b *(1/9 + 1/b) =1/6 * 36b
4b + 36 = 6b
subtract 4b from each side
36 = 2b
divide by 2
18 = b
It will take luis 18 hours
