I will use the example that they gave to describe the method
First, you need to find the difference between the new amount and the original amount. The new one is 30, while the original one is 24, so the original amount incrased by 6.
Now, you take the difference that you got, and divide it by the original amount. 6 : 24 = 1/4, or 25%. So, the percentage increase is 25%
Applying the same for the others :
32 -> 56 (increased by 24, 24:32 = 3/4 -> 75%)
15 -> 18 (increased by 3, 3:15 = 1/5 -> 20%)
30 -> 33 (increased by 3, 3:30 = 1/10 -> 10%)
150 -> 153 (increased by 3, 3:150 = 1/50 -> 2%)
120 -> 126 (increased by 6, 6:120 = 1/20 -> 5%)
200 -> 202 (increased by 2, 2:200 = 1/100 -> 1%)
