1. **State the problem:** We are given two complex numbers $Z_1 = -1 + 2i$ and $Z_2 = 2 + 3i$. We need to find their sum $Z_1 + Z_2$. 2. **Formula used:** The sum of two complex numbers $Z_1 = a + bi$ and $Z_2 = c + di$ is given by: $$Z_1 + Z_2 = (a + c) + (b + d)i$$ 3. **Apply the formula:** Here, $a = -1$, $b = 2$, $c = 2$, and $d = 3$. 4. **Calculate the real part:** $$-1 + 2 = 1$$ 5. **Calculate the imaginary part:** $$2 + 3 = 5$$ 6. **Write the final sum:** $$Z_1 + Z_2 = 1 + 5i$$ This means the sum of the complex numbers is $1 + 5i$.