Are you looking for better teaching methods?

I think so, too. This question should be told to children like this.

1. First of all, we can see that the reference object of Xiao Gang and Xiao Ming is Xiaohua. Because the language they use is "I am better than Xiaohua ..."

2. We know that the reference object Xiaohua's weight is 35kg (not equal to Xiaohua's weight, the conditions in the topic have been given directly).

3. Xiaogang's weight = Xiaohua's weight+one fifth of Xiaohua's weight.

= 35kg+35x1/5kg

= 35 kg +7 kg

= 42 kg

4. Xiaoming's weight = Xiaohua's weight-one seventh of Xiaohua's weight

= 35 kg -35× 1/7 kg

= 35 kg -5 kg

= 30 kg

I wonder if this answer is clear. Can you understand? 1/5 and 1/7 are one-fifth and one-seventh of the keyboard bombs, respectively. I hope it won't cause you misunderstanding; )

Haha, I played it all by myself!