8. Recently, an article on the internet has gone viral. It originates from a common question, as shown in Figure 1. This seemingly easy-to-solve problem actually contains profound wisdom.

Let $a, b \in\{2,3, \cdots, 8\}$. Then the maximum value of $\frac{a}{10 b+a}+\frac{b}{10 a+b}$ is $\qquad$