Question 1117544
Let {{{a}}} = number of advance tickets sold
Let {{{b}}} = number of same-day tickets sold
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(1) {{{ a + b = 50 }}}
(2) {{{ 35a + 15b = 1350 }}}
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(1) {{{ 15a + 15b = 750 }}}
Subtract (1) from (2)
(2) {{{ 35a + 15b = 1350 }}}
(1) {{{ -15a - 15b = -750 }}}
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{{{ 20a = 600 }}}
{{{ a = 30 }}}
and
(1) {{{ 30 + b = 50 }}}
(1) {{{ b = 20 }}}
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30 advance tickets were sold
20 same-day tickets were sold