If a tectonic plate has moved 125cm in a 25-year period what is its average rate of movement in cmyear?

This question depends on which plates you're talking about. Tectonic plates move in different directions and have different rates of movement. For example, the Nazca plate is moving eastward at 13.4 cm per year, but the most southern edge of the African plate is only moving northeast at 1.4 cm per year.