Final answer:
The inequality n + d ≤ 15 represents the number of nickels and dimes that Ryan has, which must be at most 15 coins altogether.
Step-by-step explanation:
To write the inequality, we need to consider the total number of coins Ryan has. Let's define the variable c as the total number of coins. Since Ryan has n nickels and d dimes, the total number of coins can be calculated by adding the number of nickels and dimes:
c = n + d.
The problem states that Ryan has at most 15 coins altogether. This means that the total number of coins, c, cannot exceed 15. So the inequality is c ≤ 15.
Substituting the expression for c, we get n + d ≤ 15. This is the inequality that represents the given information.