Question 1145678
<br>
x = rate (miles per hour) on mountain roads
3.2x = rate on country roads<br>
68/x = hours on mountain roads
192/3.2x = hours on country roads<br>
The total driving time was 6.4 hours:<br>
{{{68/x+192/3.2x = 6.4}}}
{{{68/x+60/x = 6.4}}}
{{{128/x = 6.4}}}
{{{x = 128/6.4 = 20}}}<br>
ANSWER: 20mph on mountain roads