Numeric assignment

Which of the following is/are true?
  1. A numeric expression may be used on the left side of a numeric assignment statement
  2. A numeric expression must be used on the left side of a numeric assignment statement
  3. A numeric expression may be used on the right side of a numeric assignment statement
  4. A numeric expression must be used on the right side of a numeric assignment statement
  5. A numeric variable may be used on the left side of a numeric assignment statement
  6. A numeric variable must be used on the left side of a numeric assignment statement
  7. A numeric variable may be used on the right side of a numeric assignment statement
  8. A numeric variable must be used on the right side of a numeric assignment statement
  9. One declares a numeric variable with a numeric statement
  10. One declares a string variable with a string statement
Explain your answer.