What’s the answer to this picture/question give me a simple answer

12. the amount of money in a bank account decreased by 21.5% over the last year. if the amount of money at the beginning of the year is represented by ‘n', write 3 equivalent expressions to represent the amount of money in the bank account after the decrease?

Acircle has a circumference of 28.36 units what is the diameter of the circle

Solve for n? [tex]z = \frac{3}{4} mn[/tex]