已知b/a=5/13,則a-b/a+b的值是多少

已知b/a=5/13,則a-b/a+b的值是多少

b/a=5/13,
則b=5/13a
a-b/a+b
=(a-5/13a)/(a+5/13a)
=8/13*13/18
=4/9