Answer
720
Work Step by Step
The number of permutations of {a, b, c, d, e, f, g} which end with 'a' are same as the number of permutations of {b, c, d, e, f, g} because we can append an 'a' at the end of each of its permutations to get the desired permutation.
Therefore,
The number of permutations of {a, b, c, d, e, f, g} which end with 'a'
= the number of permutations of {b, c, d, e, f, g}
= $6\times5\times4\times3\times2\times1$ or 6!
= 720