Well this is pretty simple. So the first thought is that the peanut butter would be 10$ and the jam would be 0.20$, however, the peanut butter would not be 10$ more. Instead, subtract the 10$ from the total, which gives you 0.20$, and then divide that by two. Now you have 0.10$ for each, along with another 10$ for the peanut butter. The peanut butter would be $10.10, and the jam would be 0.10$ (that's pretty cheap!).
