8. Xiao Ming saw a tractor pulling a rope on the road, moving slowly. Xiao Ming prepared to measure the length of the rope. If Xiao Ming walked in the direction the tractor was moving, from one end of the rope to the other, he took a total of 140 steps; if Xiao Ming walked in the opposite direction of the tractor, from one end of the rope to the other, he took a total of 20 steps. The speed of the tractor and Xiao Ming remained constant, and Xiao Ming could walk 1 meter per step. What is the length of the rope in meters?
【Answer】 35

【Solution】Since the first time 140 steps were taken and the second time 20 steps were taken, the time spent the first time is 7 times the time spent the second time, so the distance the tractor traveled is also in a 7 times relationship. Let the distance the tractor traveled the first time be $7 S$ meters, and the second time be $S$ meters, and let the length of the rope be $x$ meters, we get the system of equations $\left\{\begin{array}{l}x+7 S=140 \\ S+20=x\end{array} \Rightarrow\left\{\begin{array}{l}x=35 \\ S=15\end{array}\right.\right.$.