Answer:

Step-by-step explanation:
Since, there are two possible outcomes for every toss (head or tail), the sample space for a coin tossed 8 times is 2×2×2×2×2×2×2×2 = 2⁸ = 256.
Landing on heads all 8 times is just one of the possible outcomes: HHHHHHHH ⇒ 1.
Hence, the probability is calculated from its own definition:
Probability = number of favorable outcomes / number of possible outcomes