Class 9th ganit Manjari chapter 2 introduction to linear polynomials exercise 2.3 question 1

Class 9th ganit Manjari chapter 2 introduction to linear polynomials exercise 2.3 question 1 a student has Rs 500 in her savings bank account she gets Rs 150 every month as pocket money how much money will she have at the end of every month from the second month onwards find a linear expression to represent the amount she will have in the nth month.