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 59 by the denominator 2 (which you can enter in any calculator):
59 (numerator) ÷ 2 (denominator) = 29.5
And finally, you get 29.5 as your answer when you convert 21 17/2 (or 59/2) to a decimal.