a)(4.X+5):3-121:11=4
\(\Leftrightarrow\left(4x+5\right):3-11=4\)
\(\Leftrightarrow\left(4x+5\right):3=15\)
\(\Leftrightarrow4x+5=45\)
\(\Leftrightarrow4x=40\)
\(\Leftrightarrow x=10\)
b)2x+2x+3=144
\(\Leftrightarrow2^x\left(1+2^3\right)=144\)
\(\Leftrightarrow2^x=16\)
\(\Leftrightarrow2^x=2^4\)
\(\Leftrightarrow x=4\)