Question 1099588
Let {{{ a }}} = Amy's age now
Let {{{ b }}} = Anna's age now
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(1) {{{ a = 4b }}}
(2) {{{ a + 10 = 2*( b + 10 ) }}}
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Plug (1) into (2)
(2) {{{ 4b + 10 = 2b + 20 }}}
(2) {{{ 2b = 10 }}}
(2) {{{ b = 5 }}}
and
(1) {{{ a = 4b }}}
(1) {{{ a = 4*5 }}}
(1) {{{ a = 20 }}}
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Amy is 20
Anna is 5 
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check:
(2) {{{ a + 10 = 2*( b + 10 ) }}}
(2) {{{ 20 + 10 = 2*( 5 + 10 ) }}}
(2) {{{ 30 = 2*15 }}}
(2) {{{ 30 = 30 }}}
OK