You can set an equation that relates the total charges to the fixed cost and the number of miles. This is Charge (m) = 4 + 0.60 * m. Where 4 represents the fixed charge and m the numbrer of miles. In this case m = 12, which gives: Charge (12) = 4 + 0.60 * 12 = 11.2. And the answer is that Jenny will charge 11.2 sterling pounds to deliver the cakes.
