M = -9 ; solve for m by simplifying both sides of the equation, then isolating the varible
$9,900
10% off of 10,000 is 9,000
10% more than 9,000 is 9,900
There are 5280 feet in a mile:
5280ft/mi
When using proportions to solve for unknown quantities, you need to keep the same units on the same side. This means keep "ft" on the top side and "mi" on the bottom side.
I would go with the second choice.
Can you resubmit your question so that I can give you a reasonable answer
