The length of the day is α h. What is the length of the night? Find its value at α = 8; 10; 12.

Let the length of the day be a and the length of the night b. Then the sum of the length of the day and night should be equal to the length of the day, that is, 24 hours:
a + b = 24 h.
Duration of night b:
b = 24 h – a.

Answer:
1) a = 8; b = 24 h – 8 h = 16 h.
2) a = 10; b = 24 h – 10 h = 14 h.
3) a = 12; b = 24 h – 12 h = 12 h.