1/4×12/11×（11/12+3/4）
=1/4x12/11x11/12+1/4x3/4x12/11
=1/4x1+3/16x12/11
=1/4+9/44
=11/44+9/44
=20/44
=5/11
如果本题有什么不明白可以追问,