Question 735241
Let {{{ p }}} = the rate of the plane in still air
Let {{{ w }}} = the wind speed
{{{ p - w }}} = the plane's speed flying against the wind
{{{ p + w }}} = the plane's speed flying with the wind
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Against the wind:
{{{ 4200 = ( p - w )*7 }}}
With the wind:
{{{ 4200 = ( p + w )*6 }}}
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It's solvable since there are 2 equations and 2 unknowns