평행선과 각의 성질 이해하기

문제

다음 그림에서 두 직선 $l$과 $m$이 서로 평행할 때, $\angle x$의 크기를 구하시오.

\begin{tikzpicture}
  % Parallel lines
  \draw (0,0) -- (4,0) node[right] {$l$};
  \draw (0,-2) -- (4,-2) node[right] {$m$};

  % Transversal line (adjust coordinates for visual appeal)
  \draw (1.5,2) -- (3.5,-3);

  % Intersection points (approximated for clear angle marking)
  \coordinate (I1) at (2.2,0); % Intersection on line l
  \coordinate (I2) at (2.8,-2); % Intersection on line m

  % Mark 120 degree angle (upper-right at I1)
  % Need a point on transversal above I1, and a point on line l to the right of I1
  \coordinate (I1_trans_up) at ($ (I1) + (0.4, 0.7) $); % Point on transversal above I1
  \coordinate (I1_line_right) at ($ (I1) + (1,0) $); % Point on line l to the right of I1
  \	kzMarkAngle[arc=l,size=0.8cm,fill=gray!20](I1_trans_up,I1,I1_line_right)
  \
ode at ($ (I1) + (0.5, 0.4) $) {$120^\circ$};

  % Mark angle x (lower-left at I2)
  % Need a point on line m to the left of I2, and a point on transversal below I2
  \coordinate (I2_line_left) at ($ (I2) + (-1,0) $); % Point on line m to the left of I2
  \coordinate (I2_trans_down) at ($ (I2) + (-0.4, -0.7) $); % Point on transversal below I2
  \	kzMarkAngle[arc=l,size=0.8cm,fill=gray!20](I2_line_left,I2,I2_trans_down)
  \
ode at ($ (I2) + (-0.5, -0.4) $) {$\angle x$};
\end{tikzpicture}