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 12040 by the denominator 120 (which you can enter in any calculator):
12040 (numerator) ÷ 120 (denominator) = 100.33
And finally, you get 100.33 as your answer when you convert 100 40/120 (or 12040/120) to a decimal.