Exercise 4 Page 204

In an arithmetic sequence, we find each term by adding the common difference to the previous term. In the given sequence, the first term is $18$ and the common difference $\text{-}6.$ Therefore, to find the second term, we need to add $\text{-}6$ to $18.$ We can continue with this pattern to find the third and fourth terms of the sequence. Therefore, the next three terms are $12,$ $6,$ and $0.$