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

a) 

A=31–26–209+35=31–26–209+35=31−26−244=31−−218=31+218=249.

b)

B=−418−−218−−118−−318+2012    =−418−−218−−118+318+2012   =−418−−218−200+2012   =−418−−218−2212   =−418−−2430  =−418+2430  =2012.