Well, if each cake takes 2.5 cups, all you need to do is multiply 2.5 x 9 to get your answer!
In 4 hours Bethany did the whole fraction 1 of the house.
In 1 hour he would do 1/4 of it.
In 3 hours Colin did the whole fraction 1 of the house.
<span>In 1 hour he would do 1/3 of it.
</span>
In 1 hour they would both do (1/4 + 1/3)
If it takes both of them x hours to finish 1 whole fraction of the house.
In 1 hour they will both do 1/x
That means that:
1/x = 1/4 + 1/3
That is the equation. x can be solved for.
I believe the answer you are looking for is -20.
As you know, 4.78 is less than 5, so
.. yes, x=4.78 is a solution to x < 5
As you know, 6 = 6, but is not less than 6.
.. no, x=6 is not a solution to x < 6.