13. Teacher Li and three students, Xiao Ma, Xiao Lu, and Xiao Zhou, set off from the school one after another and walk along the same road to the cinema. The three students have the same walking speed, and Teacher Li's walking speed is 1.5 times that of the students. Now, Teacher Li is 235 meters away from the school, Xiao Ma is 87 meters away from the school, Xiao Lu is 59 meters away from the school, and Xiao Zhou is 26 meters away from the school. When they walk another $\qquad$ meters, the distance Teacher Li is from the school will be exactly the sum of the distances the three students are from the school.
【Analysis】Suppose the students walk another $x$ meters, at which point the distance Mr. Li is from the school is exactly the sum of the distances the three students are from the school. At this time, Mr. Li has walked another $1.5 x$ meters. We can set up the equation: $235+1.5 x=87+x+59+x+26+x \Rightarrow x=42$ That is, when the students walk another 42 meters, the distance Mr. Li is from the school is exactly the sum of the distances the three students are from the school.