3. (5 points) Think of a number, add 5 to it, multiply the result by 2, subtract 4 from the product, divide the difference by 2, and then subtract the number you initially thought of. The final calculation result is $\qquad$ .
3. (5 points) Think of a number, add 5 to it, multiply the result by 2, subtract 4, divide the difference by 2, and then subtract the number you initially thought of. The final calculation result is $\qquad$.

【Solution】Let this number be $a$,
$$
\begin{aligned}
& {[(a+5) \times 2-4] \div 2-a } \\
& =[2 a+6] \div 2-a \\
= & a+3-a \\
= & 3,
\end{aligned}
$$

Therefore, the answer is: 3.