Question

8/10 - a = 2/10 13/21 + a = 20/21 9/27 + a = 1/27 a+ 3/9 =8/9

Answer 1

8/10-2/10=a
6/10=a
a=0,6

a=20/21-13/21
a=7/21
a=1/3

a=1/27-9/29
a=-8/27
a=-0,296

a=8/9-3/9
a=5/9
a=0,(5)