Question 1156680
Let {{{ a }}} = Lee's age
Let {{{ b }}} = Lee's mother's age
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(1) {{{ b = 3a + 2 }}}
(2) {{{ a + b = 54 }}}
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Plug (1) into (2)
(2) {{{ a + 3a + 2 = 54 }}}
(2) {{{ 4a = 52 }}}
(2) {{{ a = 13 }}}
and
(1) {{{ b = 3a + 2 }}}
(1) {{{ b = 3*13 + 2 }}}
(1) {{{ b = 41 }}}
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Note that the difference in their ages
never changes. The difference is 
{{{ 41 - 13 = 28 }}}
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When Lee's age be half his mother's age:
{{{ a = ( 1/2 )*b }}}
{{{ a = ( 1/2 )*( a + 28 ) }}}
{{{ 2a = a + 28 }}}
{{{ a = 28 }}}
and
{{{ b = a + 28 }}}
{{{ b = 28 + 28 }}}
{{{ b = 56 }}}
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Lee will be 28
Lee's mother will be 56