a,\(219-7\left(x+1\right)=100\)

\(Inferred: 7\left(x+1\right)=219-100 or7\left(x+1\right)=119. \)

\(So:x+1=119\div7=17.So:x=6\)

b,\(\left(3x-6\right)\times3=3^4\)

\(Inferred : 3x-6=3^4\times3,or:3x-6=27.\)

\(So:3x=27+6\) \(or\) \(3x=33.\)

\(so\) \(end\) \(x=11\)