The price c of a used car plus 8% sales tax

1.08c or c + 0.08c

Step-by-step explanation:

The price of any used car plus 8% tax can be found by writing an expression. You can write an expression using a variable c where c is the price of the car. You will pay the 100% the whole price of the car and add on 8% of the price as tax. This means you pay 100 + 8 = 108% of the price c. This is 1.08c. Or you can also write it as c + 0.08c.

one fourth of 9% = 2.25%

gavin is correct in saying : the equivalent quarterly interest rate would be

2.25%.