Question 1068752
{{{N+D+Q=25}}} Total number of coins
{{{5N+10D+25Q=275}}} Total value of coins
.
.
{{{5Q+10N+25D=375}}} Total value of coins if they were switched
{{{10N+25D+5Q=375}}}
.
.
Using Cramer's rule,
{{{N=10}}}
{{{D=10}}}
{{{Q=5}}}