(1), and the water flow speed is x km/h.

( 12+X)×8 =( 12-X)× 12

96+8X= 144- 12X

20X=48

X = 2.4km km/h

A: The current speed is 2.4 kilometers per hour.

(2)、2(3y+4)-3=5(2y-7)

6y+8-3= 10y-35

-4y=-40

y= 10

(3) Equation 3(3x- 1)-2(6+5x)=0.

The solution is X=- 15.

Replace: -75-3(m-5)=0

Get m=-20.

(4)、40-3x=2( 15-2x)

x=- 10

y=- 10+2=-8

Substituting 3k-2( 1-2y)=5, we get k= 13.

(5) Let ten digits be x.

Then10x+6-x+18 =10 (6-x)+x.

x=2

So this two-digit number is: 24.

(6) Solution: Assume that Miss Li's home is X kilometers away from school.

So: x/40+x/30

The solution is x= 120km.

(7) If the mountain road is x meters, the flat road is 1.5 meters.

1.5x/2.5=x/2+60

The solution is x=60.

Answer: The mountain road is 60 m, and the flat road is 90 m.

(8)、