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 18870 by the denominator 125 (which you can enter in any calculator):
18870 (numerator) ÷ 125 (denominator) = 150.96
And finally, you get 150.96 as your answer when you convert 150 120/125 (or 18870/125) to a decimal.