I’ll explain it by example. Say that you have 20 cows and 5 of them are sent to slaughter, and you want to know what the percentage change for the herd is. Take 20 subtract 5 and you come up with 15. Now divide 15 by the original number of the herd (20) and you get .75. Now move your decimal place 2 places to the right to get your percentage, 75%. You have a percentage change of 75%.