Question 767663
Let {{{ m }}} = Mary Beth's age now
Let {{{ e }}} = Ellen's age now
{{{ e = 4 }}}
{{{ m = 3e }}}
{{{ m = 12 }}}
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Let {{{ n }}} = number of years from now when
Mary Beth is twice Ellen's age
{{{ m + n = 2*( e + n ) }}}
{{{ 12 + n = 2*( 4 + n ) }}}
{{{ 12 + n = 8 + 2n }}}
{{{ n = 12 - 8 }}}
{{{ n = 4 }}}
In 4 years, Mary Beth will be twice Ellen's age
check:
{{{ 12 + 4 = 16 }}}
{{{ 4 + 4 = 8 }}}
16 is twice 8
OK