虹色UFO

[0275 Q 2020/09/16(水) 17:20:53.24 ID:4sBB40MA]

3C2*4C1/9C3=｛(3*2/2*1)*(4/1)｝/｛(9*8*7)/(3*2*1)｝
=12/84
=1/7