Tính bằng cách hợp lí nhất: (1/4 + -5/13) + (2/11 + -8/13 + 3/4)

* Hướng dẫn giải

$\left(\frac{1}{4}+\frac{-5}{13}\right)+\left(\frac{2}{11}+\frac{-8}{13}+\frac{3}{4}\right)$$=\frac{1}{4}+\frac{-5}{13}+\frac{2}{11}+\frac{-8}{13}+\frac{3}{4}$ $=\left(\frac{1}{4}+\frac{3}{4}\right)+\left(\frac{-5}{13}+\frac{-8}{13}\right)+\frac{2}{11}$$=1+(-1)+\frac{2}{11}=\frac{2}{11}$