Answer
The complex conjugate of $2+3i$ is $2-3i$
When you multiply a complex number by its complex conjugate, you get a non complex number, since the result will not have any $i$s.
Work Step by Step
$(2 + 3i)(2-3i) = 2(2-3i)+3i(2-3i) = 4 - 6i +6i -9i^2 = 4 - 9(-1) = 4+9 = 13$
