So,
Let Sn be the number of streetlights at week "n".
From the given data, we can identify the following:
As you can notice, this pattern will repeat, so, it is possible to find a general formula of an arithmetic sequence:
Since we want to find the number of streetlights at the end of 38 weeks, we're going to replace the expression above by n=38:
Therefore, the answer is 206.
