Question 1026005
Look at the possible 16 outcomes and count the ones that have a red ball for 4th draw,
RRRR <--- Couldn't happen since only there is not a fourth red ball
RRRG
RRGR <--
RRGG
RGRR <--
RGRG
RGGR <--
RGGG
GRRR <--
GRRG
GRGR <--
GRGG
GGRR <--
GGRG
GGGR <--
GGGG
There are 7 possible outcomes with a fourth draw of red, so then the probability would be,
{{{P=7/16}}}