If 10^x equals 0.1 percent of 10^y, where x and y are integers, which of the following must be true?

Question: If 10^x equals 0.1 percent of 10^y, where x and y are integers, which of the following must be true?

Solution:
ATQ,
10^x = 0.1% × 10^y
⇒ 10^x = (0.1/100) × 10^y
⇒ 10^x = 0.001 × 10^y
⇒ 10^x = 1 × 10^{y - 3}
⇒ 10^x = 10^{y - 3}
⇒ x = y - 3
∴ y = x + 3