How to find the inverse function of 4x-2

Will mark brainlist what is the slope of the line passing through the points (-2, -8) and (-3,-9)? -7/5-5/71-1

Math question.. plz me .. best answer all

I'm at a bookstore with $\$35$ in my pocket and a $20\%$-off coupon. what is the cost of the most expensive book i can buy with my money and the coupon? (assume that there are books of every possible price in the bookstore. it's a large bookstore! )