A fraction is written in terms of two parts: the number on top is called the numerator and the number on the bottom is called the denominator. We can use the division method to solve this question. To get a decimal, simply divide the numerator 51 by the denominator 42:
51 (numerator) ÷ 42 (denominator) = 1.21
As a result, you get 1.21 as your answer when you convert 1 9/42 (or 51/42) to a decimal.