l = 5 + 2w.
P = 88 cm.
P = 2 ( l + w )
88 cm = 2 ( (5 + 2w) + w)
88 cm = 2 (5 + 3w)
88 cm cm = 10 + 6w
88 cm cm - 10 = 6w
78 cm = 6w
78 cm : 6 = w
13 cm = w
The width is 13 cm.
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