Question 980065
Let {{{ p }}] = number of pennies
Let {{{ d }}} = number of dimes
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(1) {{{ p + d = 13 }}}
(2) {{{ p + 10d = 94 }}} ( in cents )
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Subtract (1) from (2)
(2) {{{ p + 10d = 94 }}}
(1) {{{ -p - d = -13 }}}
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{{{ 9d = 81 }}}
{{{ d = 9 }}}
and
(1) {{{ p + d = 13 }}}
(1) {{{ p + 9 = 13 }}}
(1) {{{ p = 4 }}}
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She has 4 pennies and 9 dimes
check:
(2) {{{ p + 10d = 94 }}} 
(2) {{{ 4 + 10*9 = 94 }}} 
(2) {{{ 4 + 90 = 94 }}}
{{{ 94 = 94 }}}
OK