He has 10 pennies, 13 quarters , 21 dimes and 25 nickels.
Step-by-step explanation
Suppose, the number of pennies is

As he has 3 more quarters than pennies, 11 more dimes than pennies and 2.5 times as many nickels as pennies....
So, the number of quarters
,
the number of dimes
and
the number of nickels

We know, the value of each penny is $0.01 , value of each quarter is $0.25 , value of each dime is $0.10 and value of each nickel is $0.05
Given that, the total value of all coins is $6.70
So the equation will be.....

So, the number of pennies is 10 , number of quarters is (10+3)= 13 , number of dimes is (10+11)= 21 and number of nickels is (2.5×10)= 25