[3(x + 2).7].4 = 120
3(x + 2).7 = 120 : 4
3(x + 2) = 30 : 7
x + 2 = \(\frac{30}{7}:3\)
x = \(\frac{10}{7}-2\)
x = \(\frac{5}{7}\)
\(\left[3\left(x+2\right).7\right].4=120\)
\(\Rightarrow3\left(x+2\right)=120:4:7=\frac{30}{7}\)
\(\Rightarrow x+2=\frac{30}{7}.\frac{1}{3}=\frac{10}{7}\)
\(\Rightarrow x=\frac{10}{7}-2=-\frac{4}{7}\)
[3(x+2).7].4=120
=>3(x+2).7 = 120:4=30
=>3(x+2) = 30:7=30/7
=>x+2=30/7:3=10/7
=>x=10/7-2=-4/7
[3(x+20).7].4=120
=> 3(x+20).7=30
=> x+20 =30/21
=> x =-130/7
Vậy x = -130/7
