In this question there are numerous information's that are given for getting the required answer. The most important of those informations is that the crew of workers required 20 minutes to pave 2/15 miles of the highway. It is required to find the portion of mile these workers will pave in 1 hour. We already know that 1 hour is equal to 60 minutes. This information will help to solve the problem.
In 20 minutes the crew of workers pave = 2/15 miles
In 60 minutes the crew of same workers will pave = (2/15) * (60/20)
= (2/15) * 3
= 2/5 miles
So the crew of workers working at the same rate will pave a portion of 2/5 miles in 1 hour.