Question 1047618
Let {{{ a }}} = number of adults who went to zoo
Let {{{ b }}} = number of children who went to zoo
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(1) {{{ a + b = 72 }}}
(2) {{{ 8a + 3b  = 316 }}}
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Multiply both sides of (1) by {{{ 3 }}}
and subtract (1) from (2)
(2) {{{ 8a + 3b  = 316 }}}
(1) {{{ -3a - 3b = -216 }}}
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{{{ 5a = 100 }}}
{{{ a = 20 }}}
and
(1) {{{ a + b = 72 }}}
(1) {{{ 20 + b = 72 }}}
(1) {{{ b = 52 }}}
There were 20 adults and 52 children
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check:
(2) {{{ 8a + 3b  = 316 }}}
(2) {{{ 8*20 + 3*52  = 316 }}}
(2) {{{ 160 + 156 = 316 }}}
(2) {{{ 316 = 316 }}}
OK