<span>You would subtract the smaller amount from the larger amount.
196 - 175 = 21
21 is how many more cars he sold in 2007 than 2006. So you'll now be able to put the difference and the smaller amount into a fraction
21/175
If you simplify it (divide 21 by 175) you get 0.12. Since you need a precent, you'll times they by 100. Since 100%. 0.12 * 100 = 12. You changed by 12%. </span>