1. **State the problem:** We need to calculate the average atomic mass of neon given the isotopic distribution and their respective masses. 2. **Identify the isotopes and their abundances:** Neon-20 has a mass of 19.992 amu and represents 225 out of 250 atoms. Neon-22 has a mass of 21.991 amu and represents 25 out of 250 atoms. 3. **Calculate the fractional abundance of each isotope:** - Fraction of Neon-20 = $\frac{225}{250} = 0.9$ - Fraction of Neon-22 = $\frac{25}{250} = 0.1$ 4. **Calculate the average atomic mass by weighted sum:** $$\text{Average atomic mass} = (0.9 \times 19.992) + (0.1 \times 21.991)$$ 5. **Perform the calculations:** $$0.9 \times 19.992 = 17.9928$$ $$0.1 \times 21.991 = 2.1991$$ 6. **Add the results:** $$17.9928 + 2.1991 = 20.1919$$ 7. **Final answer:** The average atomic mass of neon is approximately $20.192$ amu.