Question 602613
C(n,r) = (n!)/(r!(n-r)!)


C(7,3) = (7!)/(3!*(7-3)!)


C(7,3) = (7!)/(3!*4!)


C(7,3) = (7*6*5*4!)/(3!*4!)


C(7,3) = (7*6*5)/(3!)


C(7,3) = (7*6*5)/(3*2*1)


C(7,3) = (210)/(6)


C(7,3) = 35


So 35 groups of 3 can be made.