Final answer:
The expression representing the amount Melanie earns each hour from babysitting, based on the expression $4x + $16 and her working for four hours, is represented by the variable $x. To determine the hourly rate, we would divide the total hourly charge by the number of hours, but the specific value of $x is not given.
Step-by-step explanation:
The given expression representing Melanie's total earnings from babysitting for four hours is $4x + $16. Here, $16 is the upfront charge and $4x represents the additional hourly charge multiplied by the number of hours worked. To find the expression representing the amount she earns each hour, we look at the variable part of the expression, which is $4x.
Since Melanie worked for four hours, this part of the expression ($4x) must account for her earnings per hour times the number of hours worked. To find her earnings per hour, we divide the total hourly charge by the number of hours. Therefore, the expression for the hourly rate is $x.
To determine the specific amount that x represents, we would need additional information, such as the total amount she earned after working the four hours. However, based on the given expression, we can conclude that x is representative of Melanie's earnings per hour.