Well, a percent is just a fraction with 100 as the denominator and the % sign after the numerator
3/4 multiplied by 25/25 = 75/100. The fraction is still the same value because 25/25 equals one and one times 3/4 = 3/4
75/100 can be written as a percent like this: 75%
This formula of turning the fraction into a fraction with a denominator of 100 and using the numerator to make the percentage works every time, but some denominators do not multiply evenly into 100, so those can be trickier. Hope this helps.