Lao Du gave Lao Gu ten rabbits, which were divided equally between the two families. Explain that Old Dolby Old Gudo 10*2=20.

Gu Jia gave Lao Du ten deer, and his family was half that of Du. At this time, Du Jia has more 10, and Gu Jia has less 10, that is, Du Jia has 20 more than Gu Jia, plus the original 20 more, * * * has 40 more than Gu Jia, and Gu Jia is half as much as Du Jia, that is, Du Jia has twice as much as Gu Jia (twice as much as Gu Jia), so much 40 is then Gu Jia.