Question 315182
I think you've got it turned around.
With the wind should be faster than against the wind.
{{{x}}}=speed of plane in still air.
{{{y}}}=speed of wind.
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Rate*Time=Distance
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{{{(x+y)4=2100}}}
1.{{{x+y=525}}}
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{{{(x-y)6=2100}}}
2.{{{x-y=350}}}
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Add equations 1 and 2 together to eliminate y and solve for x,
{{{x+y+x-y=525+350}}}
{{{2x=875}}}
{{{x=437.5}}} mph