Explicație pas cu pas:
a)
1/2+[1/4-1/8]= 1/2+[8/32-4/32]=1/2+4/32=16/32+4/32=20/32 => 10/16=> 5/8
b)
-1/3+[-1/6-1/9]= -1/3+[-9/54-6/54]= -1/3-15/54= -18/54-15/54= -33/54