Question

If planet A is four times as far from the sun as planet C, then the period of its orbit will be__ times as long

Answer 1

Within the system of the same star, the period of a planet's orbit is
proportional to the 3/2 power of its distance from the central body.
(Kepler's empirical third law of planetary motion, promoted to being
etched in stone by Newton's gravitation.)

(4) ^ 3/2 = 8 times as long.