Question 176297
If you call the number of dimes d, then the number of nickels is d+5.  The dollar amount of dimes would be 0.10d and the dollar amount of nickels would be 0.05(d+5).  So the coin back having 2.05 means
{{{0.10d+0.05(d+5)=2.05}}}
If you multiply both sides of the equation by 100, you get
{{{10d+5(d+5)=205}}} which is the first option.