If $10^{x}-10=9990$, then $x$ is equal to

![](https://cdn.mathpix.com/cropped/2024_04_20_6027bc27089ed4fc493cg-072.jpg?height=406&width=325&top_left_y=1838&top_left_x=1301)
(A) 3
(B) 5
(C) 6
(D) 4
(E) 9
Since $10^{x}-10=9990$, then $10^{x}=9990+10=10000$.

If $10^{x}=10000$, then $x=4$, since 10000 ends in 4 zeroes.

ANSWER: (D)