Question 958384
Let {{{n }}} = number of nickels
Le {{{ d }}} = number of dimes
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(1) {{{ 5n + 10d = 250 }}} ( in cents )
(2) {{{ 10n + 5d = 305 }}}
Multiply both sides of (1) by {{{2}}} and
subtract (2) from (1)
(1) {{{ 10n + 20d = 500 }}} 
(2) {{{ -10n - 5d = -305 }}}
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{{{ 15d = 195 }}}
{{{ d = 13 }}}
and
(1) {{{ 5n + 10*13 = 250 }}} 
(1) {{{ 5n + 130= 250 }}}
(1) {{{ 5n = 120 }}}
(1) {{{ n = 24 }}}
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There are 24 nickels and 13 dimes
check:
(2) {{{ 10*24 + 5*13 = 305 }}}
(2) {{{ 240 + 65 = 305 }}}
(2) {{{ 305 = 305 }}}
OK