Then AB=3x, BC=2x+ 1.

Because BD is the center line

So AD=DC=? AC=x

The ratio of the perimeters of the two parts is 8: 7.

So we can get: (AB+AD)/(BC+CD) = 8: 7.

Or (BC+CD)/(AB+AD) = 8: 7.

Substitution data (3x+x)/(2x+ 1+x) = 8: 7.

Or (2x+ 1+x)/(3x+x) = 8: 7.

Solution: x=2 or x=7/ 1 1.

AC=4 AB=6。

Or AC =14/11ab = 211.

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