2. Let the distance be y and the speed be x, and get the equation.

y/x-y/(x+ 1/6 x)= 20y/x-(72/x+(y-72)/(x+ 1/3 x))= 30

X=3.6 y=504。

3. set up first-class tea x second-class y.

y = 0.5x 24.8 * 1. 125 * 2/3 x+ 16 * 1. 125 * y-24.8 * 2/3 x- 16 * y = 460

The solution is x= 150.