Question 653645
Let {{{ n }}} = number of nickels
Let {{{ d }}} = number of dimes
given:
(1) {{{ n + d = 35 }}}
(2) {{{ 5n + 10d = 255 }}} ( in cents )
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Multiply both sides of (1) by {{{ 5 }}}
and subtract (1) from (2)
(2) {{{ 5n + 10d = 255 }}} 
(1) {{{ -5n - 5d = -175 }}}
{{{ 5d = 80 }}}
{{{ d = 16 }}}
and, since
(1) {{{ n + d = 35 }}}
(1) {{{ n + 16 = 35 }}}
(1) {{{ n = 19 }}}
He has 19 nickels and 16 dimes
check:
(2) {{{ 5*19 + 10*16 = 255 }}}
(2) {{{ 95 + 160 = 255 }}}
(2) {{{ 255 = 255 }}}
OK