Question 498494
{{{ 3*12 = 36 }}} is Mike's age now
Let {{{x}}} = number of years from now 
when uncle is twice Sally's age
(a)
{{{ 2*(12 + x) = 36 + x }}}
{{{ 24 + 2x = 36 + x }}}
{{{ x = 36 -24 }}}
{{{ x = 12 }}}
In 12 years Sally will be 24
In 12 years Uncle will be 48,
twice Sally's age
(b)
Let {{{y}}} = number of years ago when Uncle was
7 times as old as Sally
{{{ 7*( 12 - y ) = 36 - y }}}
{{{ 84 - 7y = 36 - y }}}
{{{ 6y = 84 - 36 }}}
{{{ 6y = 48 }}}
{{{ y = 8 }}}
8 years ago, Uncle was {{{ 36 - 8 = 28 }}}
8 years ago, Sally was {{{ 12 - 8 = 4 }}}
Uncle was 7 times her age