(a-b)/(a+b)=4
∴(a+b)/(a-b)=1/4
2a﹣2b/a+b-4a+4b/3a-3b
=2(a-b)/(a+b)-(a+b)/(a-b)*4/3
=2*4-1/4*4/3
=8-1/3
=23/3 7又2/3