Answer:
x = 25 mm
Explanation:
The perimeter of a rectangle is given by
P = 2(l+w) where l is the length and w is the width
We know the perimeter is 60 mm and the width is 5 mm and the length is x
60 = 2(x +5)
Divide each side by 2
60/2 = 2/2(x+5)
30 = x+5
Subtract 5 from each side
30-5 = x+5-5
25 =x
x = 25 mm