Can someone please help me with this I don’t get it please help me

Answer:
13.3
Step-by-step explanation:
The triangles are similar so we can use ratios to solve
AM AN
---------- = ------------
AM+AB AC
6 8
---------- = ------------
6+4 AC
Using cross products
6AC = 8 * 10
6AC = 80
Divide by 6
AC = 80/6
AC =13 1/3
AC = 13.33333