Question 1092811
Let {{{ x }}} = Eric's age now
{{{ x - 1 }}} = his age last year
{{{ x + 1 }}} = his age next year
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{{{ (1/4)*( x - 1 ) + 3*( x + 1 ) = 84 }}}
{{{ (1/4)*x - 1/4 + 3x + 3 = 84 }}}
{{{ ( 13/4 )*x - 1/4 = 81 }}}
Multiply both sides by {{{ 4 }}}
{{{ 13x -1 = 324 }}}
{{{ 13x = 325 }}}
{{{ x = 25 }}}
Eric is 25
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check:
{{{ (1/4)*( x - 1 ) + 3*( x + 1 ) = 84 }}}
{{{ (1/4)*( 25 - 1 ) + 3*( 25 + 1 ) = 84 }}}
{{{ (1/4)*24 + 3*26 = 84 }}}
{{{ 6 + 78 = 84 }}}
{{{ 84 = 84 }}}
OK