Explanation:
There are six unique letters. Any of the six could be the first letter. Once we've picked a first letter, that leaves 5 letters that could go second. So on and so forth. So the number of ways they can be arranged is:
6×5×4×3×2×1 = 720
The correct unscrambling is "worthy". So the probability of randomly selecting this order from the 720 possible combinations is 1/720.