Question 875611
Let {{{ n }}} = the number of nickels she has
Let {{{ q }}} = the number of quarters she has
(1) {{{ q = 3n }}}
(2) {{{ 5n + 25q= 240 }}} ( in cents )
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Substitute (1) into (2)
(2) {{{ 5n + 25*(3n)= 240 }}} 
(2) {{{ 5n + 75n = 240 }}}
(2) {{{ 80n = 240 }}}
(2) {{{ n = 3 }}}
and, since
(1) {{{ q = 3n }}}
(1) {{{ q = 3*3 }}}
(1) {{{ q = 9 }}}
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She has 3 nickels and 9 quarters
check:
(2) {{{ 5*3 + 25*9= 240 }}} 
(2) {{{ 15 + 225 = 240 }}}
(2) {{{ 240 = 240 }}}
OK