Question 833420
Convert dollar to cents
She has  450 cents
Let  {{{d}}} = the number of dimes she has
Let  {{{q}}} = the number of quarters she has
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(1) {{{ d = q + 3 }}}
(2) {{{ 10d + 25q = 450 }}}
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(1) {{{ d - q = 3 }}}
Multiply both sides of (1) by {{{25 }}}
and add (1) and (2)
(2)  {{{ 10d + 25q = 450 }}}
(1) {{{ 25d - 25q = 75 }}}
{{{ 35d = 525 }}}
{{{ d = 15 }}}
and, since
(1)  {{{ d - q = 3 }}}
(1) {{{ q = d - 3 }}}
(1) {{{ q = 12 }}}
She has 15 dimes and 12 quarters
check:
(2) {{{ 10d + 25q = 450 }}}
(2) {{{ 10*15 + 12*25 = 450 }}}
(2) {{{ 150 + 300 = 450 }}}
(2) {{{ 450 = 450 }}}
OK