We have that Linda's mean speed is 54 miles per hour. Since the total trip is 378 miles, we have the following rule of three:
[tex]\begin{gathered} 54\text{miles}\rightarrow1h \\ 378\text{miles}\rightarrow x \end{gathered}[/tex]therefore, we have:
[tex]\begin{gathered} x=\frac{378\cdot1}{54}=7 \\ x=7 \end{gathered}[/tex]Finally, we have that Linda should expect to drive 7 hours.
