22. A store increases the price of a shirt by a given percentage and then decreases the new price by the same percentage. In the end, the shirt's price is $84 \%$ of the original price. What is the given percentage? ( ).
(A) $16 \%$
(B) $20 \%$
(C) $28 \%$
(D) $36 \%$
(E) $40 \%$
22. E.

Let the given percentage be $x$. Then
$$
\begin{array}{l}
(1+x)(1-x)=0.84 \\
\Rightarrow x^{2}=0.16 \Rightarrow x=0.4 .
\end{array}
$$

Therefore, the given percentage is $40 \%$.