Answer:
4x = 30
Explanation:
You want an equation to find the side of a square (x) when the perimeter is 30 mm.
Equation
The perimeter is the sum of side lengths. When there are four sides that are all the same length (x), the perimeter is x +x +x +x = 4x. The equation will relate this to the given value of perimeter:
4x = 30
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Additional comment
The value of x is (30 mm)/4 = 7.5 mm.
In general, geometry problems like this are solved by writing equations that relate the different values given in the problem statement (or diagram). Here, the relations we used are the definition of perimeter, and the definition of a square.
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