1. We start with the problem: a) Calculate $ (1.8 \times 10^9) + (6.2 \times 10^7) $ in standard form. 2. Convert the terms so powers of 10 match for easier addition: $1.8 \times 10^9 = 1.8 \times 10^9$ $6.2 \times 10^7 = 0.062 \times 10^9$ 3. Add the coefficients: $1.8 + 0.062 = 1.862$ 4. Combine with the common power of 10: $1.862 \times 10^9$ 5. Answer for part a): $1.862 \times 10^9$ 6. Now, for part b) calculate $ (6.4 \times 10^{-11}) - (5.3 \times 10^{-12}) $ in standard form. 7. Express second term with the same power of 10: $5.3 \times 10^{-12} = 0.53 \times 10^{-11}$ 8. Subtract the coefficients: $6.4 - 0.53 = 5.87$ 9. Result in standard form: $5.87 \times 10^{-11}$ 10. Answer for part b): $5.87 \times 10^{-11}$