Question 562299
Let {{{ s }}} = Star's age now
Let {{{ d }}} = Daughter's age now
{{{ s - 7 }}} = Star's age 7 yrs ago
{{{ d - 7 }}} = Daughter's age 7 yrs ago
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(1) {{{ s - 7 = 11*( d - 7 ) }}}
(2) {{{ s = 4d }}}
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(2) {{{ d = s/4 }}}
By substitution:
(1) {{{ s - 7 = 11*( s/4 - 7 ) }}}
(1) {{{ s - 7 = (11/4)*s - 77 }}}
(1) {{{ 4s - 28 = 11s - 308 }}}
(1) {{{ 11s - 4s = 308 - 28 }}}
(1) {{{ 7s = 280 }}}
(1) {{{ s = 40 }}}
The star is 40
check:
(2) {{{ d = s/4 }}}
(2) {{{ d = 40/4 }}}
(2) {{{ d = 10 }}}
and
(1) {{{ s - 7 = 11*( d - 7 ) }}}
(1) {{{ 40 - 7 = 11*( d - 7 ) }}}
(1) {{{ 33 = 11d - 77 }}}
(1) {{{ 11d = 77 + 33 }}}
(1) {{{ 11d = 110 }}}
(1) {{{ d = 10 }}}
OK