Answer: There are 41 dimes and 11 pennies in the cup.
Explanation:
We know that 1 dime = 0.1 dollars
1 penny = 0.01 dollars
Let p be the number of pennies and d be the number of dimes.
Then we have the following equations :_
![d=4p-3..................(1)\\\\0.1d+0.01p=4.21...........(2)](https://img.qammunity.org/2020/formulas/mathematics/college/wysj8utj2drrkfqxie59x6cnppcpxlr2zt.png)
Substitute the value of d from (1) in equation (2), we get
![0.1(4p-3)+0.01p=4.21\\\\\Rightarrow\ 0.4p-0.3+0.01p=4.21\\\\\Rightarrow\ 0.41p=4.21+0.3\\\\\Rightarrow\ 0.41p=4.51\\\\\Rightarrow\ p=(4.51)/(0.41)=11](https://img.qammunity.org/2020/formulas/mathematics/college/pwrksf9h3cwhol8iif4a3qjepdk2gaya9i.png)
Then , Put value of p in (1), we get
![d=4(11)-3=44-3=41](https://img.qammunity.org/2020/formulas/mathematics/college/rukqqihb0plnlylpvh0quk6gcufttshd7j.png)
Hence, there are 41 dimes and 11 pennies in the cup.