Bài 2 (1,0 điểm). Tính hợp lý a) $\frac{15}{17}$ + $\frac{5}{13}$ + $\frac{2}{17}$ - $\frac{18}{13}$ b) $\frac{2}{5}$.$\frac{2}{9}$ + $\frac{2}{5}$ : $\frac{9}{7}$ + 2$\frac{3}{5}$

`Accnswer`

`a)15/17+5/13+2/17-18/13`

`=(15/17+2/17)+(5/13-18/13)`

`=1+(-1)`

`=0`

`---`

`b)2/5 . 2/9+2/5 :9/7+2 3/5`

`=2/5 . 2/9 +2/5 . 7/9+13/5`

`=2/5(2/9+7/9)+13/5`

`=2/5 . 1+13/5`

`=2/5+13/5`

`=15/15`

`=1`