Question 994960
Let d be the number of dimes and q be the number of quarters
{{{120 = d + q}}}
{{{120-q = d}}}

dimes are worth 10 cents, quarters are worth 25. You have a total of 2355 cents

{{{2355 = 10(120 - q) + 25q}}}
{{{2355 = 1200 - 10q + 25q}}}
{{{2355 = 1200 + 15q}}}
{{{1155 = 15q}}}
{{{77 = q}}}

With 77 quarters and a total of 120 coins, that leaves 43 dimes