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 128 by the denominator 13 (which you can enter in any calculator):
128 (numerator) ÷ 13 (denominator) = 9.85
And finally, you get 9.85 as your answer when you convert 9 11/13 (or 128/13) to a decimal.