Kiddo X.

# It took Candice 35mins. walk from his house to the park 20km away. It took her just 25mins. walk back home. What is his average speed

I used in here the formula: Speed=distance/time.
Correct me if im wrong, I got 20kph as my answer. I'm quite unsure with it. Can you please show me the correct equation/solution in this word problem. Thanks a lot!