Question 691635
The difference in their ages always
stays the same ( 26 yrs )
Let {{{ a }}} = Dad's age
Let {{{ b }}} = Lisa's age
{{{ a = 3b }}}
{{{ a - b = 26 }}}
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By substitution:
{{{ 3b - b = 26 }}}
{{{ 2b = 26 }}}
{{{ b = 13 }}}
and
Lisa is 13
check answer:
{{{ 3b = 39 }}}
{{{ a  = 3b }}}
{{{ a = 39 }}}
{{{ 39 - 13 = 26 }}}
OK