Choose the pair to go 1st in 9 ways.
Choose the pair to go 2nd in 8 ways.
Choose the pair to go 3rd in 7 ways.
Choose the pair to go 4th in 6 ways.
Choose the pair to go 5th in 5 ways.
Choose the pair to go 6th in 4 ways.
Choose the pair to go 7th in 3 ways.
Choose the pair to go 8th in 2 ways.
Choose the pair to go 9th in 1 way.
Choose the shoe order for the 1st pair 2 ways (left,right) or (right,left).
Choose the shoe order for the 2nd pair 2 ways (left,right) or (right,left).
Choose the shoe order for the 3rd pair 2 ways (left,right) or (right,left).
Choose the shoe order for the 4th pair 2 ways (left,right) or (right,left).
Choose the shoe order for the 5th pair 2 ways (left,right) or (right,left).
Choose the shoe order for the 6th pair 2 ways (left,right) or (right,left).
Choose the shoe order for the 7th pair 2 ways (left,right) or (right,left).
Choose the shoe order for the 8th pair 2 ways (left,right) or (right,left).
Choose the shoe order for the 9th pair 2 ways (left,right) or (right,left).
Answer: 9*8*7*6*5*4*3*2*1*2*2*2*2*2*2*2*2*2 = 9!*29 = 185794560.
Edwin
