A bag contains 7 green and 5 black balls. Three balls are drawn one after the other. The probability of all three balls being green, if the balls drawn are not replaced will be:

Here, n(E) =  $7C1\times 5C1\times 5C1$

And,  n(S) =  $12C1*11C1*10C1$
P(S) =  $\frac{7*6*5}{12*11*10}$ = 7/44