1. The problem asks to convert the scientific notation $6.35 \times 10^{-4}$ to a decimal number. 2. Scientific notation expresses numbers as a product of a number between 1 and 10 and a power of 10. 3. The formula to convert is: $$\text{Decimal} = a \times 10^b$$ where $a = 6.35$ and $b = -4$. 4. Since the exponent $b$ is negative, move the decimal point in $a$ to the left by 4 places. 5. Moving the decimal 4 places left: $$6.35 \to 0.000635$$ 6. Therefore, the decimal equivalent of $6.35 \times 10^{-4}$ is $0.000635$. Final answer: $0.000635$