Bethany can mow her family's lawn in 4 hours. Her brother Colin can mow the lawn in 3 hours. Which equation can be used to find the number of hours, x, it would take for Bethany and Colin to mow the lawn together?

A) 3+4 = x

B) 1/4 x - 1/3x = 1

C) 1/4x+1/3x=1

D) 4-3 = x

The answer to this is d

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.

In 1 hour he would do 1/3 of it.

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.