₆C₃ is a combination. you can find this setting in the statistics menu of your scientific calculator (i think).
If you don't have a scientific calculator, you can use the following formula:
nCr = [tex]\frac{n!}{r!(n - r)!}[/tex]
₆C₃ = [tex]\frac{6!}{3!(6 - 3)!}[/tex]
= [tex]\frac{6!}{3!(3)!}[/tex]
= [tex]\frac{6 * 5 * 4 * 3!}{3!(3)!}[/tex]
= [tex]\frac{6 * 5 * 4 }{3 * 2}[/tex]
= 5 * 4
= 20
Answer: B
