Question 1154139
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Let "v" be the speed of the wind.


Then the effective speeds of the plane are   120+v  mph  tailwind  and  120-v  against the headwind.


Therefore, the "time" equation is

    {{{490/(120+v)}}} = {{{350/(120-v)}}}


First, cancel the common factor 70 in both sides; then cross multiply. You will get

    7*(120-v) = 5*(120+v)

    840 - 7v  = 600 + 5v

    840 - 600 = 5v + 7v

    240       = 12v

      v       = 240/12 = 20.


<U>ANSWER</U>.  Speed of wind is 20 miles per hour.
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