Alexis bought x boxes of cereal for $3 each, including tax, and paid with a $20 bill. Which expression represents the total amount of change she should receive?

Expression y = 20 - 3x represents the total amount of change she should receive.

Step-by-step explanation:

Given : Alexis bought x boxes of cereal for $3 each that is including tax

This can be written mathematically as 3x.

Let the total amount of change she should receive be denoted by y

The total amount she paid is $20

The whole scenario can be written as a single expression as,

3x + y = 20

As 20 includes the cost of x boxes and the change she received (y)

y = 20 - 3x

Thus, expression y = 20 - 3x represents the total amount of change she should receive.