To convert a percent to a fraction, you have to take the number in front of the percent sign and put it over 100. So you'll basically be adding a denominator of 100 to it.
65% = 65/100
However this can be simplified further. Take a look at the factors for both numbers, and find the biggest number that both numbers have.
65 = 1, 5, 13, 65
100 = 1, 2, 4, 5, 10, 20, 25, 50, 100
The largest factor number that both numbers have is 5, therefore you can divide both 65 and 100 by 5, thereby converting the fraction into simplest form.
(65/5)/(100/5) = 13/20
So 65% as a fraction will be 13/20.
