Explanation

Let's evaluate the expressions using the given definition of a * b:

3 * 4 = 3 + 4 + (3)(4) = 3 + 4 + 12 = 19

2 * 3 = 2 + 3 + (2)(3) = 2 + 3 + 6 = 11

Now, let's subtract:

3 * 4 - 2 * 3 = 19 - 11 = 8