Question 1124508
Let {{{ a }}} = 15 cent payers
Let {{{ b }}} = 20 cent payers
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(1) {{{ a + b = 500 }}}
(2) {{{ .15a + .2b = 91 }}}
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(2) {{{ 15a + 20b = 9100 }}}
Multiply both sides of (1) by {{{ 15 }}}
and subtract (1) from (2)
(2) {{{ 15a + 20b = 9100 }}}
(1) {{{ -15a - 15b = -7500 }}}
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{{{ 5b = 1600 }}}
{{{ b = 320 }}}
And
(1) {{{ a + 320 = 500 }}}
(1) {{{ a = 180 }}}
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There were 180 15 cent payers