Answer:
The penny size d is given by the literal equation
![d=4n-2](https://img.qammunity.org/2019/formulas/mathematics/middle-school/5gze1ouozt09ibmpk61x97bdgk9gexb21g.png)
Where n is the length (in inches) of the nail.
We can deduce the value of n from equation above:
![(d+2)/4=n](https://img.qammunity.org/2019/formulas/mathematics/middle-school/gjjy997zi4e5zc623t70abdemaknpvcb06.png)
Now we have to find n with various values of d.
1. when d = 3 inches
![n=(3+2)/4](https://img.qammunity.org/2019/formulas/mathematics/middle-school/u3atk0lscysyo5q3ixe3epdvhr7atgt0ch.png)
![=>n=5/4](https://img.qammunity.org/2019/formulas/mathematics/middle-school/qulh0ptwy344wwpbpkwedjhsp68dws3igf.png)
n = 1.25 inches
2. when d = 6 inches
![n=(6+2)/4](https://img.qammunity.org/2019/formulas/mathematics/middle-school/463rje2cdqsixdckuyd76mxi7lsnu9ddl9.png)
![=>n=8/4](https://img.qammunity.org/2019/formulas/mathematics/middle-school/h9g99sjw3z8wmhne54de5okt1obmn7zdyw.png)
n = 2 inches
3. when d = 10 inches
![n=(10+2)/4](https://img.qammunity.org/2019/formulas/mathematics/middle-school/shgglisfaizf9f7zan953rlovgk4pqq15l.png)
![=>n=12/4](https://img.qammunity.org/2019/formulas/mathematics/middle-school/5qjlcunn3858y508tii7wench2r3y97af5.png)
n = 3 inches