a) $$C(3; 5)$$; $$y = kx + 4$$
$$5 = k \cdot 3 + 4$$
$$3k = 1$$
$$k = \frac{1}{3}$$
б) $$D(\frac{1}{2}; 1)$$; $$y = kx + 4$$
$$1 = k \cdot \frac{1}{2} + 4$$
$$\frac{1}{2}k = -3$$
$$k = -6$$
в) $$E(-6; -8)$$; $$y = kx + 4$$
$$-8 = k \cdot (-6) + 4$$
$$-6k = -12$$
$$k = 2$$
г) $$F(\frac{1}{3}; -8)$$; $$y = kx + 4$$
$$-8 = k \cdot \frac{1}{3} + 4$$
$$\frac{1}{3}k = -12$$
$$k = -36$$
Ответ: a) $$k = \frac{1}{3}$$; б) k = -6; в) k = 2; г) k = -36