Final answer:
There are 24 unique ways to arrange the letters in the word 'taco', calculated by the factorial of the number of letters, 4!, which equals 24.
Step-by-step explanation:
To determine how many unique ways there are to arrange the letters in the word 'taco', we use the concept of permutations. Since 'taco' consists of four different letters, we can use the formula for permutations of n distinct objects, which is n! (n factorial).
The factorial of a number n, denoted as n!, is the product of all positive integers less than or equal to n. Therefore, 4! = 4 × 3 × 2 × 1 = 24. This means there are 24 unique ways to arrange the letters in the word 'taco'.