Answer: 3 inches
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Step-by-step explanation:
The overall plank is 33 inches long. Subtract 2 copies of 2 inches off to represent those left and right 2 inches of space at each end.
33 - 2*2 = 33 - 4 = 29
So we have 29 inches to work with.
There are 4 plaques to hang up, and each is 5 inches wide. So that accounts for 4*5 = 20 inches of space just for the plaques themselves. We have 29-20 = 9 inches left for the gaps between plaques.
Since we have 4 plaques, there are 4-1 = 3 gaps between the adjacent plaques. The gap width is 9/3 = 3 inches.
See the diagram below. The values in black are the widths of each championship (5 inches each). The values in red are the gaps either between the plaques or between the plaque and the edge of the plank.
As a check, the values in that diagram should add to 33.
2+5+3+5+3+5+3+5+2 = 33
So the answer is confirmed.