0.75 as a fraction is 3/4, and it’s already in the simplest form because the numerator (3), can’t be split. Think of it as three quarters, each quarter is 25 cents, and there are three of them, so that is 75 cents, and then let’s say you are counting how many quarters you have, to get a dollar, to get a dollar, you need 4 quarters, but you only have three so it makes it 3 quarters out of 4 (3/4). Hope this helps :)