Solution: Let the original speed of A be x kilometers per hour and the speed of B be y kilometers per hour.

0.5y=3(x-y)①

0.5y=(3- 1)(x+ 1-y)②

Substitute ② into ① to get:

2x+2-2y=3x-3y

Simplify:

2(x-y)+2=3(x-y)

x-y=2③

Substitute ③ into ① to get.

0.5y=3*2

y= 12

Substitute y= 12 into ③.

x- 12=2

x= 14

∴

x= 14

y= 12

2. Solution: Assume that xKM is flat, yKM is uphill and zKM is downhill in the process of driving from A to B.

x+y+z=70①

x/30+y/20+z/40=2.5②

x/30+z/20+y/40=2.3③

Derive from ②

4x+6y+3z=300

Obtain from ③

4x+6z+3y=276

( 1 * 3)

3x+3y+3z=2 10④

②-④

x+3y=90⑤

③-④

x+3z=66⑥

⑤+⑤

2x+3y+3z= 156⑦

④-⑦ Virtue

x=54

Substitute ⑤

54+3y=90

y= 12

Substitute 6 to get

54+3z=66

z=4

∴

x=54

y= 12

z=4