So you can look at the first point and see its 5,25 so to find the rate of change you turn the 5 into a 1 by dividing 5/5 which would be 1 but you need to do the same to both sides so you divide 25 by 5 and get 5 so you have the 1 and 5 and you can turn it back to a ratio by putting : instead of the and so it would be 1:5!
