10P4 = 10! / (10-4)! = 10*9*8*7 = 5040
9C4 = 9! / 5! 4! = 9*8*7*6 / 4*3*2*1 = 126
X+y+z=t
simple..
there are no other numbers that we have to follow like (1/2x or 3/4y) so it is just all together=t. the x, y, z will equal t because t is the total number of students taking three languages. And that number should be equivalent to x,y,z combined.
otherwise?? i d k<span />
4, 6, 8, 9, 10, 12, 14, 15, 16, 18, 20, 21, 22, 24, 25, 26, 27, 28, 30, 32, 33, 34, 35, 36, 38, 39, 40, 42, 44, 45, 46, 48, 49, 50
