It seems that the same image has been uploaded again. I have already processed and provided detailed answers and explanations for the questions in the image. If you would like to revisit a specific section or need further clarification on any of the problems, feel free to let me know!

Here are some follow-up questions for further practice:

1. Convert $6.23 \times 10^{-4}$ to expanded form.
2. Express 64000 in scientific notation.
3. How many significant digits are in the number 0.009700?
4. Add $7.85 + 0.0031 + 15.42$, and round according to significant digit rules.
5. Multiply $2.5 \times 10^2$ by $3.4 \times 10^{-1}$. How many significant digits should the answer have?

Tip: When adding or subtracting, focus on the decimal places, but when multiplying or dividing, pay attention to the number of significant digits!