Hey there!
The answer to your question is Crew A
We can find this by first finding the unit rate, or acres per hour. We can divide the amount of acres by the amount of hours.
Crew A : 6/7.5 = 0.8 acres per hour
Crew B : 4.5/6 = 0.75 acres per hour
With the data above, we can see that Crew A is faster.
Hope it helps and have an amazing day! Remember, You've got this!