Question 1150414
Let {{{ n }}} = number of nickels
Let {{{ d }}} = number of dimes
Let {{{ q }}} = number of quarters
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(1) {{{ n + d + q = 30 }}}
(2) {{{ 5n + 10d + 25q = 425 }}} ( in cents )
(3) {{{ q = d }}}
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(2) {{{ 5n + 10d + 25d = 425 }}} 
(2) {{{ 5n + 35d = 425 }}}
(2) {{{ n + 7d = 85 }}}
(1) {{{ -n -2d = -30 }}} ( subtract (1) from (2)
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{{{ 5d = 55 }}}
{{{ d = 11 }}}
and
{{{ q = 11 }}}
and
(1) {{{ n + 2d = 30 }}}
(1) {{{ n + 22 = 30 }}}
(1) {{{ n = 8 }}}
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8 nickels
11 dimes
11 quarters
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check:
(2) {{{ 5n + 10d + 25q = 425 }}} 
(2) {{{ 5*8 + 10*11 + 25*11 = 425 }}} 
(2) {{{ 40 + 110 + 275 = 425 }}}
(2) {{{ 425 = 425 }}}
OK