Question 773087
Let {{{ a }}} = Gabriel's age now
Let {{{ b }}} = Grant's age now
{{{ a - 12 }}} = Gabriel's age 12 yrs ago
{{{ b - 12 }}} = Grant's age 12 yrs ago
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(1) {{{ a - 12 = 4*( b - 12 ) }}}
(2) {{{ a = 2b + 8 }}}
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Note that you mistyped:
"GRANT is eight years older than twice GRANT's age now" 
It should be:
"Gabriel is eight years older than twice grant's age now" 
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(1) {{{ a - 12 = 4b -48 }}}
(1) {{{ a - 4b = -36 }}}
and
(2) {{{ a - 2b = 8 }}}
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Subtract (1) from (2)
(2) {{{ a - 2b = 8 }}}
(1) {{{ -a + 4b = 36 }}}
{{{ 2b = 44 }}}
{{{ b = 22 }}}
and, since
(2) {{{ a - 2b = 8 }}}
(2) {{{ a - 2*22 = 8 }}}
(2) {{{ a = 44 + 8 }}}
(2) {{{ a = 52 }}}
Gabriel is 52 now
check:
(1) {{{ a - 12 = 4*( b - 12 ) }}}
(1) {{{ 52 - 12 = 4*( 22 - 12 ) }}}
(1) {{{ 40 = 4*10 }}}
(1) {{{ 40 = 40 }}}
Ok
(2) {{{ a = 2b + 8 }}}
(2) {{{ 52 = 2*22 + 8 }}}
(2) {{{ 52 = 44 + 8 }}}
(2) {{{ 52 = 52 }}}
OK