\(\Rightarrow124-\left(20-4x\right)=120\\ \Rightarrow20-4x=24\\ \Rightarrow4x=-4\\ \Rightarrow x=-1\)
[ 124 - ( 20 - 4x ) ] : 30 = 4
=> [ 124 - ( 20 - 4x ) ] : 30 = 4
=> 124 - ( 20 - 4x ) = 120
=> 20 - 4x = 124 - 120
=> 20 - 4x = 4
=>4x = 20 - 4
=>4x = 16
=> x = 16 : 4
=> x = 4
Vậy x = 4 .
\(\left[124-\left(20-4x\right)\right]:30=4\)
\(\Leftrightarrow20-4x=4\)
hay x=4