Ok, so we know he has 18 coins of quarters and dimes.
Which all equal up to $2.70.
As I estimate, there could be 7 dimes and 8 quarters. But 8 + 7 = 15, so that means there are more than 7 dimes and less than 8 quarters-- but still equal all to the value of $2.70.
~Time skip~
As I did my math, this is a very intruging problem and interesting problem. It isn't 6 dimes and 7 quarters cause that equals to $2.35.
~Time skip~
I fillany found the answer by my little brother who also was interested with this question (who is smarter than me sadly), and I was quite surprised. So, the answer would be...
12 dimes = $1.20
6 quarters = $1.50
$1.20 + $1.50 = $2.70.
(Plus, this was so hard, thanks little bro)
So, 6 more dimes than quarters.