Everyone, not only when in school, needs time to time to convert between fractions, decimals, and percentages - in any way.

To make it quick and easy, let's check first how it works when we'll compare the basics:

1/2 = 0.5 = 50%

Fractions to decimals: simple dividing (because fraction line means dividing, good to know, right?) - if you don't know it straight (like me let's say - because I know how to convert many fractions without thinking - simply by using the conversion so often, that I remember their decimal notation) divide it either on paper (more effort, but always possible) or with calculator (when you have it)

Decimals to percentages: multiplying by 100 - because percentage literally means value per one hundred. And multiplying by one hundred is very easy, just "move" the decimal point two positions to the right (to make bigger number, not smaller)

Percentages to fractions: the best way is, go to decimals first, as written below:

Percentages to decimals: that means reversal operation to the multiplying before, divide by one hundred ("move" decimal point two positions to the left, to make smaller number)

Decimals to fractions: if you don't know straight again the fractional notation of the decimal, write it first as a fraction of an appropriate power of ten (tenths would be over 10, hundredths over 100, etc.) and simplify it, if possible, afterwards

Fractions to percentages: closing the circle, again, is better to go through one additional step - using decimals first, as described above already.

One important note at the end, which I believe is worth to mention - the example above expresses still the same number, just in different notation. That's why it's all equal, that's why I used equal signs between all three (notations of the) numbers.