Answer: 286 possibilities
Step-by-step explanation:
It's a combination because the order of countries doesn't matter in this scenario.
[tex]_{n} C_{r} =\frac{n!}{r!(n-r)!}=\frac{13!}{10!(13-10)!}=\frac{13!}{10!(3)!}=\frac{13!}{10!(3)!}\\\\=\frac{6227020800}{3628800(6)}=\frac{6227020800}{3628800(6)}=\frac{6227020800}{21772800}=286[/tex]
I hope this is right