Hãy tìm x biết: ​\(- \left( { - x} \right) + \left( { - 9} \right) + 75 + \left( { - 19} \right) + \left( { - 21} \right) = - 5\)

* Hướng dẫn giải

 \(\begin{array}{l}\ \, - \left( { - x} \right) + \left( { - 9} \right) + 75 + \left( { - 19} \right) + \left( { - 21} \right) = - 5\\\,\,\,x + \left( { - 9} \right) + 75 + \left( { - 19} \right) + \left( { - 21} \right) = - 5\\\,\,\,x + 66 + \left( { - 19} \right) + \left( { - 21} \right) = - 5\\\,\,\,x + 47 + \left( { - 21} \right) = - 5\\\,\,\,x + 26 = - 5\\\,\,\,x = \left( { - 5} \right) - 26\\\,\,\,x = \left( { - 5} \right) + \left( { - 26} \right)\\\,\,\,x = - 31\end{array}\)