Question 757704
Let {{{ n }}} = number of nickels he has
Let {{{ d }}} = number of dimes he has
given:
(1) {{{ d = n + 8 }}}
(2) {{{ 10d + 5n = 305 }}} ( in cents )
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(1) {{{ d - n = 8 }}}
Multiply both sides by {{{ 5 }}}
and add (1) and (2)
(1) {{{ 5d - 5n = 40 }}}
(2) {{{ 10d + 5n = 305 }}}
{{{ 15d = 345 }}}
{{{ d = 23 }}}
and, since
(1) {{{ d = n + 8 }}}
(1) {{{ 23 = n + 8 }}}
(1) {{{ n = 23 - 8 }}}
(1) {{{ n = 15 }}}
He has 15 nickels and 23 dimes
check:
(2) {{{ 10*23 + 5*15 = 305 }}} 
(2) {{{ 230 + 75 = 305 }}}
(2) {{{ 305 = 305 }}}
OK