Line AB = 12cm, point m is the midpoint of AB, point C is on MB and MC: CB = 2:1, find the length of line AC?

Line AB = 12cm, point m is the midpoint of AB, point C is on MB and MC: CB = 2:1, find the length of line AC?

AM=MB=AB/2=12/2=6,
MC=2/3MB=2/3*6=4,
AC=AM+MC=6+4=10.