Please help and no links! Mike receives a $40,000 salary for working as an administrator. If Mike spends 90% of his salary on expenses each year, then how much money does Mike have to spend on expenses? Thank you!

Suppose you are an avid reader and are looking to save money on the cost of books instead of paying about $20 for each book, you decide to look into purchasing a kindle for $120 you can purchase e-books for about $5 each 1. find the slope-intercept equation for the cost of the hard copy of books using x to represent the number of books 2. find the slope-intercept equation for the cost of the kindle with cost of e-books using x to represent the number of books

Precalculus question, image attached.

What is the equation of the line that is parallel to the line with the equation y= -3/4x +1 and passes through the point (12,-12)