In the figure, AB=5cm, BC=4cm and AC=7 cm. If BX bisects ABC, calculate the length of AX. Please give full exp

In the figure, AB=5cm, BC=4cm and AC=7 cm. If BX bisects ABC, calculate the length of AX. Please give full explanation. what is why.. how is what
Diagram: check this link for figure
http://www.urch.com/forums/gmat-math/136863-geometry-problem-helpppppppppp-urgentttt.html#post883603

I was unable to enlarge the sketch enough to see it clearly, but I expect this problem is based on the fact that the bisector of an angle of a triangle divides the opposite side in the ratio of the other two sides.
In this case, that means
AX:XC = AB:BC = 5:4
i.e. divide 7 cm in the ratio 5:4
Hence AX = (5/9)*7
................ = 35/9 cm
................ = 3.889 cm
and XC = 3.111 cm