Question 703941
Let {{{ k }}} = Kierra's age now
Let {{{ b }}} = the building's age now
given:
(1) {{{ k = 3b }}}
(2) {{{ k + 20 = 2*( b + 20 ) }}}
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Substitute (1) into (2)
(2) {{{ 3b + 20 = 2*( b + 20 ) }}}
(2) {{{ 3b + 20 = 2b + 40 }}}
(2) {{{ b = 40 - 20 }}}
(2) {{{ b = 20 }}}
And, since
(1) {{{ k = 3b }}}
(1) {{{ k = 3*20 }}}
(1) {{{ k = 60 }}}
Kierra is 60
check answer:
(2) {{{ k + 20 = 2*( b + 20 ) }}}
(2) {{{ 60 + 20 = 2*( 20 + 20 ) }}}
(2) {{{ 80 = 2*40 }}}
(2) {{{ 80 = 80 }}}
OK