y = 10x+ 13 = 12x-3

2x= 13+3

x=8

y= 10*8+ 13=93

The length of the road from this mountain to that mountain is x meters.

x/60+x/80=70

x/6+x/8=700

4x+3x=700*24

x=2400

The road from this mountain to that mountain is 2400 meters long.

3. Need to add X white balls

(7+x)/24=5/3

7+x=24*(5/3)=40

x=33

Need to add 33 white balls.

4. Party A and Party B meet for x kilometers.

[(x/2)/6]/{[(x/2)-60]/6}=4/3

(x/2)/[(x/2)-60]=4/3

4*[(x/2)-60]=3*(x/2)

2x-240=3x/2

x/2=240

x=480

Party A and Party B meet 480 kilometers.