Which property of equality would you use -to solve the equation math8n=16

How do you use the additive inverse to evaluate an expression that uses subtraction in a full sentence

Suppose that the price p (in dollars) and the weekly sales x (in thousands of units) of a certain commodity satisfy the demand equation 4p cubedplusx squaredequals38 comma 400. determine the rate at which sales are changing at a time when xequals80, pequals20, and the price is falling at the rate of $.20 per week.

Jacks bank statement shows an account balance of -$25.50. which describes the magnitude, of size, of the debt in dollars