Answer:
1/4 + 1/3 = 1/x
Step-by-step explanation:
"Bethany can mow her family’s lawn in 4 hours."
In 1 hour, she does 1/4 of the job.
"Her brother Colin can mow the lawn in 3 hours."
In 1 hour, he does 1/3 of the job.
When they work together, in 1 hour they do 1/4 + 1/3 of the job.
When they work together, they can mow the lawn in x hours.
In 1 hour, they do 1/x of the job. This means that 1/4 + 1/3 must equal 1/x.
1/4 + 1/3 = 1/x
