数字推理:1/4,3/10,(),2/5 A.23/50 B.17/40 C.11/30 D7/20 急,

问题描述:

数字推理:1/4,3/10,(),2/5 A.23/50 B.17/40 C.11/30 D7/20 急,

D7/20怎么得的,谢谢!5/20, 6/20, 7/20, 8/20