You could put it as 38/50 and you can multiply 50 by 2 to get 100 but whatever you do to the bottom you have to do to the top so you have to multiply 38 by 2. 38x2 is 76 so you get 76/100 and the is 76%.
Or you can divided the numerator by the denominator. Then multiply by 100 and thats your percent. 38 divided by 50= 0.76. 0.76 x 100 is 76%