Find the unit rate: divide the area by the time. Optionally: convert the given fractions into decimal fractions to speed things up:
0.4 acre
--------------- = 0.5333.... acre/hour, or 8/15 acre/hour.
0.75 hour
We can use a proportion to solve this problem
2/5 acre ---- 3/4 h
x acre --------1 h
x= ((2/5)*1) / (3/4)= (2/5) *(4/3) = 8/15 acre
