A. When substracting numbers in parenthesis, you distribute the negative out front if one is present. (11-9i)-(15-12i) to (11-9i)+(-15+12i). You can then write the numbers without parenthesis, and solve. 11 - 9i - 15 + 12i to -4+3i. Remember, you can only add and subtract like terms! 3i and 2 could not be subtracted together, as 2 does not have an i with it.