Question

鸡比兔多20只,鸡的脚比兔的脚少40只,鸡兔各多少只?

Answer 1

设鸡有X只,兔有（X-20)只.

4（X-20)-2X=40

4X-80-2X=40

4X-2X=40+80

2X=120

X=60

X-20=60-20=40只