Question 1048618
Let {{{ q }}} = number of quarters
Let {{{ d }}} = number of dimes
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(1) {{{ q + d = 18 }}}
(2) {{{ 25q + 10d = 240 }}} ( in cents )
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(2) {{{ 5q + 2d = 48 }}}
Multiply both sides of (1) by {{{2}}}
and subtract (1) from (2)
(2) {{{ 5q + 2d = 48 }}}
(1) {{{ -2q - 2d = -36 }}}
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{{{ 3q = 12 }}}
{{{ q = 4 }}}
and
(1) {{{ q + d = 18 }}}
(1) {{{ 4 + d = 18 }}}
(1) {{{ d = 14 }}}
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There are 4 quarters and 14 dimes
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check:
(2) {{{ 25q + 10d = 240 }}} 
(2) {{{ 25*4 + 10*14 = 240 }}} 
(2) {{{ 100 + 140 = 240 }}}
(2) {{{ 240 = 240 }}}
OK