25. Incorrect. The answer is false, not true. According to
the inverse function rule, if given y = f(x), the inverse function x = f^{-1}(y)
exists, then dx/dy = (dy/dx)^{-1}. Therefore, since the inverse demand
function P = 6 - 2Q exists, then dP/dQ = (dQ/dP)^{-1} = (-0.5)^{-1}
= -2.