а+(2а-b-a+1) = a+2a-b-a+1=2a-b+1

2b-(a+b-3a-2)=2b-a-b+3a+2=2a+b+2

3a-(a-(a-2b))=3a-(a-a+2b)=3a-a+a-2b=3a-2b

4b+(b-(a+3b))=4b+(b-a-3b)=4b+b-a-3b=2b-a