Question 1106988
Let {{{ n }}} = the number of 5 cent coins
Let {{{ d }}} = the numbe of 10 cent coins
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(1) {{{ n + d = 71 }}}
(2) {{{ 5n + 10d = 560 }}} ( in cents )
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Multiply both sides of (1) by {{{ 5 }}} and 
subtract (1) from (2)
(2) {{{ 5n + 10d = 560 }}}
(1) {{{ -5n - 5d = -355 }}}
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{{{ 5d = 205 }}}
{{{ d = 41 }}}
and
(1) {{{ n + 41 = 71 }}}
(1) {{{ n = 30 }}}
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The number of 5 cent coins is 30
The number of 10 cent coins is 41