Let's start off with the probability to draw a blue marble which is basically the number of blue marbles/ total number of marbles = 8/16=1/2= 50%, now the red marble, since we already drawn a marble the total number of marbles decreases by 1 so the probability of drawing a red marble is 2/15, now we take 1 out again so the total is 14 so the probability of drawing a blue marble again is 7/14*1/2=1/4= 25% hope this helps!
