7. Given seven numbers $60, 100, x, 40, 50, 200, 90$ with an average and median both equal to $x$. Then $x$ is ().
(A) 50
(B) 60
(C) 75
(D) 90
(E) 100
7. D.

Since the average of the seven numbers is $x$, then
$$
\begin{array}{l}
\frac{60+100+x+40+50+200+90}{7}=x \\
\Rightarrow 7 x=540+x \Rightarrow x=90 .
\end{array}
$$

Substituting $x=90$ we get
$$
40, 50, 60, 90, 90, 100, 200 \text {. }
$$

At this point, 90 is also the median. Hence $x=90$.