So we know that the bag has total 15 cookies, and 1 cookie that does not have any raisin. Finally, the probability that one cookie won't have any raisin is 1/15 or 7 percent. Hope it help!
You would use the Pythagorean there on which is a^2+b^2=c^2, from there you plug int what they gave you and solve for b, and b=12
