\(a,2x-138=2^3-3^2\)
\(2x-138=8-9\)
\(2x-138=-1\)
\(2x=-1+138\)
\(2x=137\)
\(x=137:2\)
\(x=68,5\)
\(Vậyx=68,5\)
\(b,\left[3.\left(x+2\right):7\right].4=120\)
\(3x+6:7=120:4\)
\(3x+\frac{6}{7}=30\)
\(3x=30-\frac{6}{7}\)
\(3x=\frac{204}{7}\)
\(x=\frac{204}{7}:3\)
\(x=\frac{204}{7}.\frac{1}{3}\)
\(x=\frac{68}{7}\)
\(Vậyx=\frac{68}{7}\)
\(c,\left\{\left[\left(2x+14\right):2^2-3\right]:2\right\}-1=0\)
\(\left\{\left[\left(2x+14\right):4-3\right]:2\right\}=0+1\)
\(\left[\left(2x+14\right):4-3\right]:2=1\)
\(\left(2x+14\right):4-3=1.2\)
\(\left(2x+14\right):4-3=2\)
\(\left(2x+14\right):4=2+3\)
\(\left(2x+14\right):4=5\)
\(2x+14=5.4\)
\(2x+14=20\)
\(2x=20-14\)
\(2x=6\)
\(\Rightarrow x=6:2\)
\(x=3\)
\(Vậyx=3\)
