Question 327157
P is the number of pennies, N is the number of nickels, D is the number of dimes.
1.{{{D=2P-6}}}
2.{{{D=N=2P-6}}}
3.{{{1P+5N+10D=840}}}
{{{P+5(2P-6)+10(2P-6)=840}}}
{{{P+10P+20P-30-60=840}}}
{{{31P=930}}}
{{{highlight(P=30)}}}
.
.
.
{{{D=N=2(30)-6}}}
{{{highlight(D=N=54)}}}