Question 35053
4 options:
RRRB
RRBR
RBRR
BRRR


Look at RRRB ans assuming there is no replacement of marbles during this process:
First out is red: P = 5/12
second out is red: P = 4/11
third out is red: P = 3/10
fourth out is black: P = 7/9


--> P = {{{ (5/12)*(4/11)*(3/10)*(7/9) }}}


Now look at RRBR:
--> P = {{{ (5/12)*(4/11)*(7/10)*(3/9) }}}
which if you look closely is the same thing as RRRB


So, in total we have 4 versions of the same thing 
--> P = {{{4 (5/12)*(4/11)*(3/10)*(7/9) }}}
--> P = {{{ (4*5*4*3*7)/(12*11*10*9) }}}
--> P = {{{ (4*5*7)/(11*10*9) }}}
--> P = {{{ (4*7)/(11*2*9) }}}
--> P = {{{ (2*7)/(11*9) }}}
--> P = {{{ 14/99 }}}
--> P = 0.141414


jon.