Tính giá trị các biểu thức sau: a) A=31–[26–(209+35) b) B=−418−{−218−[−118

* Hướng dẫn giải

a) 

$$\begin{gathered} A=31–\left[26–\left(209+35\right)\right] \\ \begin{array}{l}=31–\left[26–\left(209+35\right)\right]\\ =31-\left[26-244\right]\\ =31-\left(-218\right)\\ =31+218\\ =249.\end{array} \end{gathered}$$

b)

$$\begin{gathered} B=-418-\left\{-218-\left[-118-\left(-318\right)+2012\right]\right\} \\ \begin{array}{l}=-418-\left\{-218-\left[-118+318+2012\right]\right\}\\ =-418-\left\{-218-\left[200+2012\right]\right\}\\ =-418-\left\{-218-2212\right\}\\ =-418-\left(-2430\right)\\ =-418+2430\\ =2012.\end{array} \end{gathered}$$