We will determine the number of square miles he mows as follows:
[tex]A=(2\frac{1}{2})(2\frac{3}{4})\Rightarrow A=(\frac{4}{2}+\frac{1}{2})(\frac{8}{4}+\frac{3}{4})[/tex][tex]\Rightarrow A=(\frac{5}{2})(\frac{11}{4})\Rightarrow A=\frac{55}{8}\Rightarrow A=6\frac{7}{8}\Rightarrow A=6.875[/tex]So, he mows 55/8 square miles for each park.