Help please!

2-digit numbers less than 91 which are 1 less than a multiple of 10

Desmond wants to sell his car that he paid $8,000 for 2 years ago. the car depreciated, or decreased in value, at a constant rate each month over a 2-year period. if x represents the monthly depreciation amount, which expression shows how much desmond can sell his car for today? 8,000 + 24x 8,000 − 24x 8,000 + 2x 8,000 − 2x

What number should be added to both sides of the equation to complete this square? x^2-10x=7