Let be "x" the amount of money (in dollars) you would save with the discount.
By definition, a percent can be converted to a Decimal number by dividing it by 100. Then, since the cake store is having 25% off sale on all cakes, this can be written as:
According to the information given in the exercise, the regular price of the cake you want is $9. Based on this, you can set up the following expression for price of the cake with the discount (in dollars):
Evaluating, you get:
Knowing this value, you can set up that:
Finally, evaluating, you get:
The answer is: You would save $2.25 with the discount.