Respuesta :

starxin
If we consider it as a combination problem, then we could calculate the how many combinations are there if we pick up three nodes out of six nodes, and then we have:
[tex] C_{6}^{3}= \frac{6*5*4}{3*2*1} =20[/tex]
And the answer should be 20

Answer:

4

Step-by-step explanation: