A=-1/6+5/3+1/2
=-1/6+10/6+3/6
=12/6
=2
B= 13 - [12 - 4 x (-1) - 7] x (5 - 7,5)
=13-(12+4-7)*(-2.5)
=13-9*(-2.5)
=13+22.5
=35.5
C=3/8(-2/5)+3/5(-7/4)
=-6/40-21/20
=-3/20-21/20
=-24/20
=-6/5
D=(2-2/5):(4/5*9)
=(10/5-2/5):36/5
=8/5:36/5
=8/5*5/36
=8/36
=2/9