[tex] \frac{11}{13}+ \frac{1111}{1313}+ \frac{111111}{131313}+ \frac{11111111}{13131313}= \\ = \frac{11}{13}+ \frac{11*101}{13*101}+ \frac{11*10101}{13*10101}+ \frac{11*1010101}{13*1010101}= \\ = \frac{11}{13}+ \frac{11}{13}+ \frac{11}{13}+ \frac{11}{13}= \\ = \frac{44}{13} [/tex]
