Answer:
'-18' is the constant in the expression -18 - 3a.
Explanation:
We know that in an algebraic expression the constant term has a fixed value and it can not be changed.
For example,
The expression x + 2 contains two terms, x and 2. Here, '2' is a constant term because it has a fixed value and cannot be changed.
IN OUR CASE,
Given the expression
-18 - 3a
As '-18' is a fixed number and its value can not be changed.
Therefore, '-18' is the constant in the expression -18 - 3a.