a) 28/12-35/15=7/3-7/3=0
b) 2/3:(-12)= - 2/3 ×1/12)=-1/18
c) 2:(-1/4)=- 2×4=-8
d) 63/40 x 64/27=7/5 x 8/3=56/15
e) (0,2)³=(2/10)³=8/1000=1/125=0,008
f) (0,8)²=(8/10)²=(4/5)²=16/25=0,64
g) 0,(8) × 3=8/9×3=8/3
h) 0,(5)+0, (4)=5/9+4/9=9/9=1
i) [-0,(6)]²=
(6/9)²=(2/3)²=4/9