Răspuns:
C.30 cm
Explicație pas cu pas:
[tex] ABC, E\in [AB], F\in [AC], EF || BC _{\implies}^{\text{Teorema lui Thales}} \frac{AE}{EB} = \frac{AF}{FC}\implies EB = AE\cdot \frac{FC}{AF} = 10\cdot \frac{8}{4} = 10\cdot 2 = 20\:cm\\\\ AB = AE + EB = 10 + 20 = 30\:cm[/tex]