Connor has $9.00 in dimes and quarters. if he has twice as many quaters as dimes, how many of each coin does he have?

So since we have a relationship between quarters and dimes, let's use dimes=d

This says that dimes(0.1 dollars) and twice as many dimes(quarters so 0.25) is 9 dollars. So it is

Combining we get

Dividing by 0.6 we get

Since there are twice as many quarters as dimes, the answer is 15 dimes and 30 quarters.