arsenlevadniy

Verified answer

1) (a-10)+3=8,
a-10=8-3,
a-10=5,
a=5+10,
a=15;

(a-10)+3=8,
a-10+3=8,
a-7=8,
a=8+7,
a=15;

2) 6+(3+a)=20,
3+a=20-6,
3+a=14,
a=14-3,
a=11;

6+(3+a)=20,
6+3+a=20,
9+a=20,
a=20-9,
a=11;

3) 10-(2+b)=8,
2+b=10-8,
2+b=2,
b=2-2,
b=0;

10-(2+b)=8,
10-2-b=8,
8-b=8,
b=8-8,
b=0.