1。 Assuming that the highway can be completed within t years after the completion of B, and the length of the highway is 1, then the speed of A is 1/3 and the speed of B is 1/2, then,

1/2× 1/3+( 1/2+ 1/3)t = 1

T=5 years

2。 Suppose there are x people transferred to a, then there are (20-X) people transferred to b.rule.

27+X=2[ 19+(20-X)]

X = 17 of the solution,

So, 20- 17=3 people transferred to B.

3。 Let the distance between the two places be x kilometers, 12 minutes = 1/5 hours, and 7 minutes =7/60 hours.

X/6- 1/5=X/5+7/60

Multiply both sides of the equation by 60,

Yes,10x-12 =12x+7.

The solution x = 9.5km.

4。 If A's current age is X, B's current age is Y, and the age difference between A and B is (X-Y) years, then

Y-(X-Y)= 10，X+(X-Y)=25

To solve this system of equations, X=20 years old, Y= 15 years old,

So the age difference between A and B is 20- 15=5 years old.