To find the value of 15 nickels using the expression 5n, you substitute 15 for n and multiply 5 by 15, resulting in 75 cents.
The expression 5n represents the value, in cents, of n nickels.
If you want to find the value of 15 nickels, you simply substitute 15 for n in the expression, so it becomes 5 × 15.
To compute the value, you multiply 5 by 15, which equals 75.
Therefore, the value of 15 nickels is 75 cents.