The cost to gift wrap an order is $3 plus $1 per item wrapped . what is the independent and dependent variable

The independent variable for this function is the number of items wrapped while the dependent variable is the cost to wrap the gifts. This is because the independent variable refers to the input to the function while the dependent variable is the output of the function. In this case, the function is expressed as:

C = 3 + 1(X)

where, 

C = cost of wrapping the gifts
X = number of items wrapped