Question 936957
(1) {{{ p + n + d  = 18 }}}
(2) {{{ p = 3d }}}
(3) {{{ n = 2d }}}
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Substitute (2) and (3) into (1)
(1) {{{ 3d + 2d + d = 18 }}}
(1) {{{ 6d = 18 }}}
(1) {{{ d = 3 }}}
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(2) {{{ p = 3d }}}
(2) {{{ p = 3*3 }}}
(2) {{{ p = 9 }}}
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(3) {{{ n = 2d }}}
(3) {{{ n = 2*3 }}}
(3) {{{ n = 6 }}}
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There are 9 pennies, 6 nickels, and 3 dimes
check:
(1) {{{ p + n + d  = 18 }}}
(1) {{{ 9 + 6 + 3  = 18 }}}
(1) {{{ 18 = 18 }}}
OK