(4/10-1)·(3 1/3-2,5)/(1 3/4)=(-6/10)·( 3 1/3-2 1/2) /(1 3/4)=(-3/5)·(3 2/6-2 3/6)/(1 3/4)=
=(-3/5)·5/6: 1 3/4=(-3/5)·5/6:7/4=-(3/5)·5/6·4/7=-2/7
