Final answer:
Alex mistakenly wrote 103.903 in expanded form, and the correct way to write it is explained.
Step-by-step explanation:
When writing a number in expanded form, we express each digit in the number as a separate term, multiplied by the appropriate power of 10. In this case, Alex made a mistake by incorrectly breaking down 103.903. He should have written it as 100 + 3 × 10 + 9 × 0.01 + 1 × 0.001.
To correct Alex's mistake, we need to express each digit in the number as a separate term, multiplied by the appropriate power of 10. The correct expanded form of 103.903 is 100 + 3 × 10 + 9 × 0.1 + 1 × 0.001.