Solution:
Speed, s, can be calculated using the formula;
[tex]\begin{gathered} s=\frac{d}{t} \\ \\ \text{ Where;} \\ d=distance,t=time \end{gathered}[/tex]Thus;
[tex]\begin{gathered} d=7.5miles,t=3hours \\ \\ s=\frac{7.5miles}{3hours} \\ \\ s=25\frac{miles}{hour} \end{gathered}[/tex]ANSWER: Her speed is 25 miles per hour.