Question 1034779
Let {{{ m }}} = Mum's age now
Let {{{ d }}} = daughter's age now
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(1) {{{ m = 4d }}}
(2) {{{ m + 4  = 3*( d + 4 ) }}}
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Substitute (1) into (2)
(2) {{{ 4d + 4  = 3*( d + 4 ) }}}
(2) {{{ 4d + 4 = 3d + 12 }}}
(2) {{{ d = 8 }}}
and
(1) {{{ m = 4d }}}
(1) {{{ m = 4*8 }}}
(1) {{{ m = 32 }}}
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Let {{{ x }}} = the number of years from now
when Mum's age is twice daughter's age
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(3) {{{ m + x  = 2*( d + x ) }}}
(3) {{{ 32 + x  = 2*( 8 + x ) }}}
(3) {{{ 32 + x = 16 + 2x }}}
(3) {{{ x = 16 }}}
In 16 years Mum will be twice daughter's age
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check:
{{{ 32 + 16 = 48 }}}
and
{{{ 8 + 16 = 24 }}}
48 is twice 24
OK