Question 335081
Let N be the number of nickels, D the number of dimes.
1.{{{N+D=20}}}
2.{{{5N+10D=140}}}
From eq. 1,
{{{D=20-N}}}
Substitute into eq. 2,
{{{5N+10(20-N)=140}}}
{{{5N+200-10N=140}}}
{{{-5N+200=140}}}
{{{-5N=-60}}}
{{{highlight(N=12)}}}
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There are 12 nickels in the purse.