Question 1143420
Looks like they want you to use only 
the single variable, {{{ x }}}
{{{ x }}} = Darius' age now
{{{ x + 87 }}} = Jack's age now
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{{{ x + 87 - 11 = 4*( x - 11 ) }}}
{{{ x + 76 = 4x - 44 }}}
{{{ 3x = 120 }}}
{{{ x = 40 }}}
Darius is 40 now
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check:
{{{ x + 87 - 11 = 4*( x - 11 ) }}}
{{{ 40 + 87 - 11 = 4*( 40 - 11 ) }}}
{{{ 116 = 4*29 }}}
{{{ 116 = 116 }}}
OK