Question 1134921
Let {{{ a }}} = the price of an adult ticket
Let {{{ b }}} = the price of a student ticket
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(1) {{{ 10a + 17b =74 }}}
(2) {{{ 10a + 21b = 142 }}}
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subtract (1) from (2)
{{{ 4b = 68 }}}
{{{ b = 17 }}}
and
(1) {{{ 10a + 17*17 = 74 }}}
(1) {{{ 10a = 74 - 289 }}}
{{{ a }}} can't be negative. I think maybe the
problem was copied wrong.  Please check.