Does anyone know how to do this?

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?

How many quarts of a 50% solution of acid must be added to 20 quarts of a 20% solution of acid in order to get a 40% solution of acid?

Th perimeter of a rectangular garden is 150 feet. the length is 50 feet longer than the width, w. which equation could be used to calculate the width of the garden? a.) 2w+ 2(w-50) =150 b.) 2w+50 + 2w =150 c.) 2(w+50) + w =150 d.) 2w+ 2(w + 50) = 150 need asap. will give brainliest !