Which of the following best describes a linear demand curve equation?

If the demand equation is P = 500 - 3Q, what does the coefficient -3 represent?

Given the supply equation P = 100 + 4Q, rearrange the equation to isolate Q.

Given the demand equation P = 700 - 5Q and the supply equation P = 200 + 2Q, find the equilibrium quantity.

Suppose you are given the demand equation as P = 900 - 3Q and the supply equation as Q = 2P - 100. Which approach would be more efficient to find equilibrium, and why?