Question 1: Make the high-speed rail x kilometers long.

Equation 3/5x= 1/2x+25

Solution: x=250

The high-speed rail is 250 kilometers long.

Question 2: Suppose there are 5x girls and 6x boys.

Equation 5X+5=8/9×6x

Solution: x= 15

5x=75

There are 75 girls.

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