Question 897155
Let {{{ a }}} = number of 1 br apts
Let {{{ b }}} = number of 2 br apts
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(1) {{{ a + b = 12 }}}
(2) {{{ 360a + 450b = 4950 }}}
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(2) {{{ 12a + 15b = 165 }}}
Multiply both sides of (1) by {{{ 12 }}}
and subtract (1) from (2)
(2) {{{ 12a + 15b = 165 }}}
(1) {{{ -12a - 12b = -144 }}}
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{{{ 3b = 21 }}}
{{{ b = 7 }}}
and
(1) {{{ a + b = 12 }}}
(1) {{{ a + 7 = 12 }}}
(1) {{{ a = 5 }}}
The number of 2 br apts is 7
check:
(2) {{{ 360*5 + 450*7 = 4950 }}}
(2) {{{ 1800 + 3150 = 4950 }}}
(2) {{{ 4950 = 4950 }}}
OK