原式=6/11(7/8-5/12)=6/11*(11/24)=1/4
6/11*7/8-5/12*6/11
=6/11*7/8-5/11*6/12
=6/11*7/8-5/11*1/2
=6/11*7/8-5/11*4/8
=(6*7-5*4)/(11*8)
=22/88=1/4
(6/11)×(7/8)-(5/12)×(6/11)
=(6/11)×[(7/8)-(5/12)]
=(6/11)×[(21/24)-(10/24)]
=(6/11)×(11/24)
=6/24
=1/4
6/11*(7/8-5/12)=1/4