A fraction is usually split into two parts: the first part is the number on top, called the numerator; and the second part is the number on the bottom, called the denominator. These are both separated by a line called the “divisor line”. We can use the division method help to solve this question: to get a decimal, simply divide the numerator 4581 by the denominator 79 (which you can enter in any calculator):
4581 (numerator) ÷ 79 (denominator) = 57.99
And finally, you get 57.99 as your answer when you convert 57 78/79 (or 4581/79) to a decimal.