Mathematics

Problem

\triangle ABC

, points

D

and

E

are on

AB

and

AC

respectively with

DE\parallel BC

. Points

F

AD

and

G

AE

are chosen so that

FG\parallel DE

. Given

AD = 6\,\text{cm}

DB = 12\,\text{cm}

AF = 3\,\text{cm}

and

AC = 21\,\text{cm}

, find the length of

AG

. a)

7\text{ cm}

3\text{ cm}

3.5\text{ cm}

4.5\text{ cm}