(2/3-3/4+1/12-5/6)*(-12)=-2/3x12+3/4x12-1/12x12+5/6x12=-8+9-1+10=10-3×(-4/7)+2又2/7×(-3)+1/7×(-3)=3x(4/7-2-2/7-1/7)=3x-13/7=-39/7
(2/3-3/4+1/12-5/6)*(-12)