3. A 3x3 grid as shown in Figure 1, each small square is filled with a complex number, and the sum of the complex numbers in each row, each column, and each diagonal is equal. Then the complex number represented by $x$ is $\qquad$ .



Preserving the original text's line breaks and format, the translation is as follows:

3. A 3x3 grid as shown in Figure 1, each small square is filled with a complex number, and the sum of the complex numbers in each row, each column, and each diagonal is equal. Then the complex number represented by $x$ is $\qquad$ .
3. $\frac{1}{2}+\frac{1}{2} \mathrm{i}$.

Let the numbers in the other two cells of the first row be $y$ and $z$ (as shown in Figure 3). According to the problem, the sum of the three numbers in each row, each column, and each diagonal is $x+y+z$. Therefore, the middle cell is $x+z-1$, the first cell in the middle row is $y-i+1$, the first cell in the third row is $z+\mathrm{i}-1$, and the first cell in the third row on the right is $x+y-\mathrm{i}$. Finally, by the sum of the three numbers on the diagonal containing $x$, we get
$$
x+(x+z-1)+(x+y-\mathrm{i})=x+y+z .
$$

Solving this, we get $x=\frac{1}{2}+\frac{1}{2} \mathrm{i}$.