Question 853105
A Barrel contains {{{ highlight_green(22)}}} balls: 12 yellow and 10 red 
P={{{(12C3)(10C4)/(22C7)= 220*210/170544 = .2709}}}
where: {{{nCx = (n!)/x!(n - x)!) = 220*}}} 
Ex: 12C3 = {{{12*11*10*cross(9*7*6*5*4*3*2)/((3*2)*cross(9*7*6*5*4*3*2))= 12*11*10/(3*2) = 220}}}