Question 189437
Let {{{a}}}= number of adult tickets sold
Let {{{s}}}= number of student tickets sold
given:
(1) {{{a + s = 321}}}
(2) {{{3.5a + 2.5s = 937.5}}}
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Multiply both sides of (1) by {{{2.5}}} and
subtract (1) from (2)
(2) {{{3.5a + 2.5s = 937.5}}}
(1) {{{-2.5a - 2.5s = -802.5}}}
(3) {{{a = 135}}}
135 adult tickets were sold
check answer:
(1) {{{a + s = 321}}}
(1) {{{135 + s = 321}}}
(1) {{{s = 186}}}
and
(2) {{{3.5a + 2.5s = 937.5}}}
(2) {{{3.5*135 + 2.5*186 = 937.5}}}
(2) {{{472.5 + 465 = 937.5}}}
(2) {{{937.5 = 937.5}}}
OK