Starting with super easy questions is a good way to start the study of mathematics. Unfortunately, it can also lead people astray.

You paper shows that you crossed out the zeros in the bottom part of the first fraction and in the top part of the second number. This only works when the second number is divisible by 100. only 1% of all integers are evenly divided by 100.

It would not work if the number was something like 555.

The nice thing about percentages is that one can calculate them just by shifting a decimal point by two numerals.

20% of 555 would be equal to 0.20 * 555 or 20 * 5.55 which is 111. I usually just multiple the numbers together and then move the decimal point two positions. 20 & 555 = 11100. Moving the decimal point reveals 111