 একটি সংখ্যা  অন্যটির দ্বিগুণের চেয়ে ৯ কম, এবং তাদের যোগফল ৪২। বড় সংখ্যাটি কত।
To solve this problem, let's analyze it step-by-step:

Step-1: Let, two numbers are X and Y, where X > Y

Step-2: Sum of these numbers is 42. So, X+Y=42

Step-3: According to the question, twice of the smaller number is 9 less than the larger one. So, 2Y-9 = X or, X = 2Y-9

Step-4: We have to find the larger number (X).

Step-5: Now, X + Y = 42
                     ->Y = 42-X
And from step-3 we find, X = 2Y-9
       -> X = 2*(42-X) - 9
       -> X = 2*42 – 2X - 9 
       -> X = 84 – 2X - 9
       -> X + 2X = 84 - 9
       -> 3X = 75
       -> X = 75/3
       -> X = 25
So, the larger number is 25.

#Answer: 25