Question

A pen costs `11 and a notebook costs `13. find the number of ways in which a person can spend exactly `1000 to buy pensand notebooks.

Answer 1

X be no of pens and y be no of notebooks
So 
11x+13y=1000
Now find different values of x and y

Answer 2

Here, We can use a linear equation in 2 variables

that is,
11x+13y=1000
hope it is correct