If the coin is flipped 250 times, and lands on tails 120 times, set this up as a fraction. Put 250 on the bottom, and 120 on the top (because you want to know percentage of tails for 250 coin flips) to get 120/250. This is 0.48, to turn this into a percentage multiply by 100, 48%. You can check this answer by taking 0.48(250) and you will get 120.