Tính: a) 5/7 - (-3,9) b) (-3,25) + 4 3/4

* Hướng dẫn giải

$$\begin{gathered} a) \frac{5}{7}-(-3,9)=\frac{5}{7}+\frac{39}{10}{ \\ }^{}=\frac{50}{70}+\frac{273}{70}=\frac{323}{70} \end{gathered}$$

$$\begin{gathered} b) (-3,25)+4\frac{3}{4}=\frac{-325}{100}+\frac{19}{4} \\ =\frac{-13}{4}+\frac{19}{4}=\frac{6}{4}=\frac{3}{2} \end{gathered}$$