\(126+\left(-20\right)+|124|-\left(-320\right)-|-150|\)
\(=126-20+124+320-150\)
\(=\left(126+124\right)+\left(320-20\right)-150\)
\(=250-150+300=100+300=400\)
\(126+\left(-20\right)+|124|-\left(-320\right)-|-150|\)
=126-20+124+320-150
=(126+124)+(320-150-20)
=250+150
=400