First we have to find out how much the car's price increased by. So we subtract the original value from the increased value: 25,920 - 18,000 = 7,920. Next we divide 7,920 by 2, since it's a two year period and the question is asking for one year: 7,920 ÷ 2 = 3,960. Now that we know how much it increased (3,960), we put that in a fraction over our original value (18,000) to find out the actual rate of increase:
$${\frac{{\mathtt{3\,960}}}{{\mathtt{18\,000}}}} = {\frac{{\mathtt{11}}}{{\mathtt{50}}}} = {\mathtt{0.22}}$$ Multiplying 0.22 by one hundred, we get 22%.