Question 1191175
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(a)  One of the 7 pictures is fixed;  6 other can be arranged in any order in the remaining 6 positions.


     The answer is 6! = 6*5*4*3*2*1 = 720 possible permutations.




(b)  6! + 6! = 720 + 720 = 1440 possible permutations / arrangements.


     First   720 arrangements with the specified picture at the left end, and

     another 720 arrangements with the specified picture at the right end.
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Solved, answered and explained.