Question 861356
Let {{{ a }}} = number of 3 kg bags used
Let {{{ b }}} = number of 2 kg bags used
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(1) {{{ 3a + 2b = 112 }}}
(2) {{{ b = 2a }}}
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By substitution:
(1) {{{ 3a + 2*( 2a ) = 112 }}}
(1) {{{ 7a = 112 }}}
(1) {{{ a = 16 }}}
and, since
(2) {{{ b = 2a }}}
(2) {{{ b = 32 }}}
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There are 16 of the 3 kg bags and
32 of the 2 kg bags