\(150-x=42-\left(15-7\right)\)
\(\Leftrightarrow150-x=42-15+7\)
\(\Leftrightarrow150-x=34\)
\(\Leftrightarrow x=150-34\)
\(\Leftrightarrow x=116\)
150-x=42-8
150-x=34
x=150-34=116
150 -x = 42 - ( 15 - 7 )
150 - x = 42 - 8
150 - x = 34
x = 150 - 34
x = 116