Question 445448
Let {{{a}}} = number sold @ $35 each
Let {{{b}}} = number sold @ $45 each
given:
(1) {{{ a + b = 16 }}}
(2) {{{ 35a + 45b = 630 }}}
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Multiply both sides of (1) by {{{35}}}
and subtract (1) from (2)
(2) {{{ 35a + 45b = 630 }}}
(1) {{{ -35a - 35b = -560 }}}
{{{ 10b = 70 }}}
{{{ b = 7 }}}
and, since
(1) {{{ a + b = 16 }}}
(1) {{{ a + 7 = 16 }}}
(1) {{{ a = 9 }}}
The number sold @ $35 each is 9
The number sold @ $45 each is 7