<|system|>
The areas of three squares are 16, 49 and 169.  What is the average (mean) of their side lengths?</s>.
<|user|>
Can you answer based on context?
<|assistant|>
Since the areas of the three squares are 16, 49 and 169, then their side lengths are $\sqrt{16}=4$, $\sqrt{49}=7$ and $\sqrt{169}=13$, respectively.

Thus, the average of their side lengths is $$\frac{4+7+13}{3}=8.$$