What is the slope of any line perpendicular to the graph of y=-5x+7

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

Omar is going on a road trip! the car rental company offers him two types of cars. each car has a fixed price, but he also needs to consider the cost of fuel. the first car costs $90 to rent, and because of its fuel consumption rate, there's an additional cost of s0.50 per kilometer driven.

If 5x - 2 = -12, then x = a) -50 b) -4.4 c) -2.8 d) -2