Question

Mary can clean a house in two hours, Gina can clean a house in three hours.
How long would it take for Mary and Gina to clean the house together.

Answer 1

Also please explain how you got the answer.

Answer 2

consider how much of the job gets done in one hour.

Mary does 1/2
Gina does 1/3

So, ever hour, 1/2 + 1/3 = 5/6 of the job gets done.

If 5/6 gets done in one hour, the whole job takes 6/5 hours.

1/2 + 1/3 = 1/x

For further discussions, I refer you to

(a) your class text
(b) your teacher
(c) google: algebra work problems

Answer 3

Mary's rate = house/2
Gina's rate = house/3
combined rate = house/2 + house/3
= 5house/6 , (just like 1/2 + 1/3 = 5/6)

time at combined rate = house/(5house/6)
= house(6)/(5house)
= 6/5

notice that "house" canceled, we could have used anything, some would just use 1