8. (5 points) As shown in the figure, a square wall with a side length of 50 meters. Person A and Person B start from points $A$ and $C$ respectively at the same time, moving along the wall in a clockwise direction. It is known that A walks 5 meters per second, and B walks 3 meters per second. Then, they will walk to the same side of the square after at least $\qquad$ seconds.
【Analysis】Person A is at point $A$, and person B is at point $B$. The distance between A and B is $50 \times 2=100$ (meters); When A walks from $A$ to $C$, it takes $100 \div 5=20$ (seconds); In 20 seconds, B walks $3 \times 20=60$ (meters), reaching point $D$ and exceeding $D$ by $60-50=10$ (meters), walking on the side $AD$; A takes $50 \div 5=10$ (seconds) to walk from $C$ to $D$; In 10 seconds, B walks $3 \times 10=30$ (meters); At this point, B exceeds $D$ by $10+30=40$ (meters), still on the side $AD$, and A is also on the side $AD$; Therefore, the total time used is $10+20=30$ (seconds).

【Solution】Solution: (1) The time it takes for A to walk from $A$ to $C$:
$$
50 \times 2 \div 5=20 \text { (seconds); }
$$
(2) The distance B walks in 20 seconds:
$$
3 \times 20=60 \text { (meters), }
$$

At this point, B is on the side $AD$;
(3) The time it takes for A to walk from $C$ to $D$:
$$
50 \div 5=10 \text { (seconds); }
$$

At this point, both A and B are on the side $AD$.
(4) Total time used:
$$
10+20=30 \text { (seconds). }
$$

Answer: It takes at least 30 seconds for A and B to walk to the same side of the square.
The answer is: 30.