Let the uphill from A to B be Xkm, the flat road be Ykm, and the downhill road be Zkm, then X+Y+Z=3.3.

①X/3

+

Y/4

+

Z/5

=

5 1/60

②Z/3

+

Y/4

+

X/5

=

53.4/60

③ 20x+15y+12z = 51is obtained from equation ②.

④ 20Z+ 15Y+ 12X=53.4.

⑤ Z-X=0.3 from ⑤-④, then Z=X+0.3.

⑥ Bring ⑥ formula into ⑥ formula to get X+Y+X+0.3=3.3, then Y=3-2X.

⑦ Formula ⑦ is brought into formula ⑦, 20x+15 (3-2x)+12 (x+0.3) = 51,so X= 1.2, so y = 0.6 and z =/kloc-.

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