Tính B = -1 1/12 : (1/4 - 1/3) -1 1/15 : (1/5 - 1/3)

* Hướng dẫn giải

$$\begin{gathered} B=-1\frac{1}{12}:\left(\frac{1}{4}-\frac{1}{3}\right)-1\frac{1}{15}:\left(\frac{1}{5}-\frac{1}{3}\right) \\ =\frac{-13}{12}:\left(\frac{-1}{12}\right)-\frac{16}{15}:\left(\frac{-2}{15}\right) \\ =13+8 \\ = 21 \end{gathered}$$