Final answer:
To determine the value of the monomial -15a for a given value of 'a', substitute the value into the monomial and multiply by -15. If 'a' equals 3, then -15a equals -45.
Step-by-step explanation:
To find the value of the monomial -15a when a is given a specific value, you simply multiply -15 by the value of 'a'. Assuming that the value of 'a' has been provided (the question does not specify what 'a' is), you replace 'a' with its given value and then perform the multiplication.
For example, if the value of 'a' is 3, then:
-15a = -15 × 3 = -45
This result represents the value of the monomial -15a when a = 3. Remember to substitute the given value into the monomial and follow the rules of multiplication for negative numbers.