Explanation:
a) Let 'm' represents score in a Mathematics test. The variable has a fixed value because the marks Sarah obtained in her test will not change
b) Let 'd' represent the distance between the Zen house and the school. The variable has a fixed value because by using the same route, the distance will always remain constant.
c) Let 't' represent the temperature on the summit of Mount Everest. The variable has a changed value because the temperature may alter depending on the time of day and also climatic conditions which will affect the temperature.