Answer:
x = 8
Explanation:
The perimeter (P) is calculated as
P = 2(l + b) ← l is length and b is breadth
Here l = 12 and b = x , P = 40, then
2(12 + x) = 40 ( divide both sides by 2 )
12 + x = 20 ( subtract 12 from both sides )
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