Question 1085263
Let {{{ a }}} = Jan's age now
Let {{{ b }}} = Anna's age now
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(1) {{{ a = b + 7 }}}
(2) {{{ 2*( a + b ) = 66 }}}
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(2) {{{ 2a + 2b = 66 }}}
(2) {{{ a + b = 33 }}}
Plug (1) into (2)
(2) {{{ b + 7 + b = 33 }}}
(2) {{{ 2b = 26 }}}
(2) {{{ b = 13 }}}
and
(1) {{{ a = b + 7 }}}
(1) {{{ a = 13 + 7 }}}
(1) {{{ a = 20 }}}
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Jan is 20
Anna is 13
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check:
Jan is 7 years older than Anna. 
TRUE
double the sum of their combined ages is 66
{{{ 2*( 20 + 13 ) = 66 }}}
{{{ 2*33 = 66 }}}
{{{ 66 = 66 }}}
OK