解:5/13÷(1/5+5/13),=5/13÷(13/65+25/65),=5/13÷38/65,=5/13×65/38,=25/38
=5/13×5+5/13×13/5=25/13+1=38/13
5/13÷(1/5+5/13)=5/13÷(13/65+25/65)=5/13÷38/65=5/13×65/38=25/38