SOLUTION: A publisher printed acertain number of book if He Has Printed 2000 copies more each copy would have cost of rupees 5 less. If he had printed 1600 copies less then each copy wo

Let N be the number of copies and p be the price for one single copy in the base scenario.

Then the condition gives you this system of 2 non-linear equations


Np = (N+2000)*(p-5),              (1)
Np = (N-1600)*(p+10),             (2)


It is equivalent to

Np = Np + 2000p -  5N - 10000,    (1')
Np = Np - 1600p + 10N - 16000.    (2')


Simplifying it, you get

 2000p - 5N = 10000,              (1'')
-1600p + 10N = 16000.             (2'')



This system is just a linear, and you can easily solve it by using the Elimination method:


 4000p - 10N = 20000              (1''')
-1600p + 10N = 16000              (2''')
-----------------------------Add the equations

 2400p       = 36000  ====>  p =  = 15.


Then from eq(2''')  10N = 16000 + 1600*15 = 40000  ====>  N = 4000.


Answer.  N= 4000,  p= 15.