To determine the cost of each pen, we can set up an equation based on the information provided. Amir bought a comic book for $9 and four pens, and his total expenditure was $25.
- Let \( p \) represent the cost of each pen.
- The total cost for four pens is \( 4p \).
- The equation representing the total spending is:
\[ 9 + 4p = 25 \]
Now, we can solve for \( p \):
- Subtract 9 from both sides of the equation:
\[ 4p = 25 - 9 \]
\[ 4p = 16 \]
- Divide both sides by 4:
\[ p = \frac{16}{4} \]
\[ p = 4 \]
So, each pen costs $4.