Write \( -8 \frac{9}{10} \) as a decimal number.

To convert \( -8 \frac{9}{10} \) into a decimal, first convert the mixed number to an improper fraction. This gives you \( -8 - \frac{9}{10} \) or \( -8.9 \) when combined. So, \( -8 \frac{9}{10} \) as a decimal is \( -8.9 \). Remember, when you convert fractions, simply divide the numerator by the denominator. In this case, \( \frac{9}{10} = 0.9 \), making it super easy to see how a fraction can be neatly transformed into its decimal form. Keep practicing with mixed numbers, and you'll master them in no time!