\(55-5.\left(20+11\right)=55-5.31=55-155=-100\)
=55-(5.20)-5.11
=55-100-55
=55-55-100
=0-100
=-100
\(55-5\left(20+11\right)\)
\(=55-\left(5.20+5.11\right)\)
\(=55-\left(100+55\right)\)
\(=55-100-55\)
\(=55+\left(-100\right)+\left(-55\right)\)
\(=\text{ }\left[55+\left(-55\right)\right]+\left(-100\right)\)
\(=0+\left(-100\right)\)
\(=-100\)