Question 591501
Let {{{ s }}} = the bird's speed with no wind
{{{ s + w }}} = bird's speed going with the wind
{{{ s - w }}} = bird's speed going against the wind
------------
going with the wind:
{{{ 12 = ( s + w )*1 }}}
going against the wind:
{{{ s - w = 4 }}}
{{{ s = 4 + w }}}
By substitution:
{{{ 12 = ( 4 + w + w )*1 }}}
{{{ 12 = 4 + 2w }}}
{{{ 2w = 12 - 4 }}}
{{{ 2w = 8 }}}
{{{ w = 4 }}}
and
{{{ s = 4 + w }}}
{{{ s = 4 + 4 }}}
{{{ s = 8 }}}
The speed of the wind is 4 mi/hr
The speed of the bird with no wind is 8 mi/hr