\(\begin{array}{rclcl} 3 \cdot 4^x + 3 \cdot 4^x + 3 \cdot 4^x & = & 36 & \\ 9 \cdot 4^x & = & 36 & \qquad | & /\,9 \\ 4^x & = & 36\,/\,9 & \\ 4^x & = & 4 & \\ x & = & 1 & & \\ \end{array}\)