This is a question of simple division. Only thing is the numerator is big and so dividing requires the numerator to be made small. For that purpose it is required to divide the numerator and denominator by 10 and then the numerator becomes small and can be divided by the denominator without the help of calculator.
2580 divided by 20 is what needs to be found.
2580/20 = 258/2
= 129
129 is the required answer and hopefully this will come to your help.