Question 1197567
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Here is a very unorthodox solution method -- in case you are interested in looking at alternatives.<br>
Let x be the speed of the wind; then the plane's speeds are 150+x with the wind and 150-x against the wind.<br>
The distances are the same, so the ratio of speeds is the reciprocal of the ratio of the times.  The ratio of the two times in minutes is 168/120 = 7/5.  So<br>
{{{(150+x)/(150-x)=7/5}}}
{{{5(150+x)=7(150-x)}}}
{{{750+5x=1050-7x}}}
{{{12x=300}}}
{{{x=25}}}<br>
ANSWER: The wind speed is 25mph<br>