Jerry and Kuba are laying a hardwood floor. Working alone, Jerry can do the job in 21 hr. If the two of them work together, they can complete the job in 12 hr. How long would it take Kuba to lay the floor working alone?

28 hours

Step-by-step explanation:

If Jerry alone can do the job in 21 hours, the amount of the job completed per hour is 1/21.

If Jerry and Kuba work together, they can do the job in 12 hours, so the amount of the job completed per hour is 1/12.

If the speed of Jerry is is J and the speed of Kuba is K, we have that:

J = 1/21

J + K = 1/12

1/21 + K = 1/12

4/84 + 84K/84 = 7/84

4 + 84K = 7

84K = 3

K = 3/84 = 1/28

If Kuba can do 1/28 of the job per hour, He can complete the job alone in 28 hours.

step- i d k and i d c : )

you: : 0

bye

#12 the answer is the third option