What's a statement that is true for any number or variable

The variable in a relation who’s value depends on the value of the independent variable is called what?

Evaluate the expression for the given value of the variable 2×(c2-5) for c=4

Marla bought a book for $12.95, a binder for $3.49, and a backpack for $44.99. the sales tax rate is 6%. find the amount of tax and the total she paid for these items