You can find percentages with a calculator, or without a calculator:
Non-calculator: To find a percentage of a number without a calculator, you divide the number by the percentage's number equivalent. For example, to find 10% of a number you divide by 10, to find 25% of a number you divide by 4 (because 25% is 1/4 of 100%), to find 50% you divide by 2, and 1% is dividing by 100, etcetera. You can then use the initial percentage's to find more complex percentages, so to find 30% you would divide by 10 and then multiply that by 3, and 75% would be dividing by 4 and multiplying that be 3.
Calculator: If you have a calculator when you are asked to find the percentage, there is a much simpler way. All percentages have a decimal equivalent because you can picture all percentages as being fractions over 100, and therefore if you divide that number by 100 you get its decimal. On a calculator, if you multiply a number by a decimal multiplier, you get that percentage. For example, if you want to find 25% of a number on a calculator, you would multiply that number by 0.25.
I hope this explains things well enough! Let me know if I missed anything out :)
