if her average speed is 3.3 miles per hour, that means in 1 hour, she was covering 3.3 miles, now, how many miles in 2.25 hours?
[tex]\bf \begin{array}{ccll} miles&hours\\ \cline{1-2} 3.3&1\\ m&2.25 \end{array}\implies \cfrac{3.3}{m}=\cfrac{1}{2.25}\implies m=\cfrac{3.3\cdot 2.25}{1}=m\implies 7.425=m[/tex]