Bài 1: (1,0 điểm) Thực hiện phép tính: a) A= $\frac{-3}{13}$- $\frac{7}{17}$+ $\frac{-5}{19}$+ $\frac{-10}{13}$ + $\frac{24}{17}$- $\frac{14}{19}$  b) B= $1,25.\frac{7}{19}$+ $\frac{5}{4}$. $\frac{15}{19}$- $1\frac{1}{4}$. $\frac{3}{19}$ 

Bài `1:`

`A= (-3)/13 - 7/17 + (-5)/19 + (-10)/13 + 24/17 - 14/19`

`A= -(3/13+10/13) - (5/19 + 14/19) + (24/17 - 7/17)`

`A= - 1 - 1 + 1`

`A= -2  +1`

`A= -1`

Vậy `A=-1`

`B= 1,25 . 7/19 + 5/4 . 15/19 - 1 1/4 . 3/19`

`B= 5/4 . 7/19 + 5/4 . 15/19 - 5/4 . 3/19`

`B= 5/4. (7/19 + 15/19 - 3/19)`

`B= 5/4.1`

`B=1`

Vậy `B=1`