Question 768990
Let {{{ d[1] }}} = distance she traveled at {{{ 50 }}} mi/hr
{{{ d[2] = 185 - d[1] }}} = distance she traveled at {{{ 55 }}} mi/hr
{{{ d[1] / 50 + d[2] / 55 = 3.5 }}}
{{{ d[1] / 50 + ( 185 - d[1] ) / 55 = 3.5 }}}
Multiply both sides by {{{ 50*55 }}}
{{{ 55d[1] + 50*( 185 - d[1] ) = 3.5*50*55 }}}
{{{ 55d[1] + 9250 - 50d[1] = 9625 }}}
{{{ 5d[1] = 375 }}}
{{{ d[1] = 75 }}}
and
{{{ 185 - 75 = 110 }}}
She traveled 75 mi at 50 mi/hr
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check:
{{{ d[1] / 50 + d[2] / 55 = 3.5 }}}
{{{ 75 / 50 + 110 / 55 = 3.5 }}}
{{{ 3/2 + 2 = 3.5 }}}
{{{ 3.5 = 3.5 }}}
OK