Standard Form

Move the decimal point 4 places to the left to create 2.5, which is between 1 and 10. Since you moved 4 places, multiply by $10^4$ to get $2.5\times 10^4$.

Multiply 2 and 3 to get 6. Then, add the powers of 10: $10^6\times 10^{-4}=10^2$. Combine to get $6\times 10^2$.

Move the decimal point 3 places to the right to create 4.5, which is between 1 and 10. Since you moved 3 places, multiply by $10^{-3}$ to get $4.5\times 10^{-3}$.

Multiply 5 and 4 to get 20. Add the powers of 10: $10^3\times 10^{-7}=10^{-4}$. Since 20 is not between 1 and 10, rewrite it as $2\times 10^1$, then combine with $10^{-4}$ to get $2\times 10^{-3}$.

Move the decimal point 5 places to the left to create 6.7, which is between 1 and 10. Since you moved 5 places, multiply by $10^5$ to get $6.7\times 10^5$.

Multiply 8.2 by 2.5 to get 20.5. Add the powers of 10: $10^6\times 10^{-4}=10^2$. Since 20.5 is not between 1 and 10, adjust to $2.05\times 10^3$.