-2/3-1/6-(-1/4)-1/2=-5/6+1/4-1/2=-5/6-1/4=-13/4(-11又三分之二)-(-7又五分之二）-12又三分之一减去（-4.2）=-11又2/3+7.4-12又1/3+4.2=(-11又2/3-12又1/3)+11.6=-24+11.6=-12.4(-3)/[(-2/5）/（-1/4）]=-3÷8/5=-...