Tìm x biết ​(x:left( { – 12} right) + 4 = 31)

Ta có:

(begin{array}{l} x:left( { – 12} right) + 4 = 31\ x:left( { – 12} right) = 31 – 4\ x:left( { – 12} right) = 27\ x = 27.left( { – 12} right)\ x = – 324 end{array})