Joanna's house is 8000 feet due west of her school. If her house is assigned the position of zero and her school is assigned the position of + 8000, what would be Joanna's position if she walked 100 feet west of her house?

Joanna's position would be - 100.

Explanation:

Joanna's position would be 100 feets west to her house. Her position is negative because Joanna walked west of her house. The position would have been positive if she had moved east of his house, that is, to the school.