Answer:
There are 11 pennies and 41 dimes in the cup.
Step-by-step explanation:
Let the pennies be represented by = p
Let the dimes be represented by = d
The total value of the coins is $4.21. We get the first equation as:
.......(1)
The number of dimes is three less than four times the number of pennies. We get the second equation as:
......(2)
Substituting the value of d from (2) in (1)

Solving this we get;

=> 
=> 
We get p = 11
And
= 
We get d = 41
Therefore, there are 11 pennies and 41 dimes in the cup.