Answer: Equation that represents this problem is

The base of the triangle is 34.5 mm.
Explanation:
Let b represents the base length of the triangle in mm.
Given : The height of a triangle is 5 more than double the base length.
i.e. Height = 2b+5
If the height of the triangle is 74 mm, then the equation that represents this problem is

To find b , first subtract 5 from both sides of the equation, we get
[Divide both sides by 2]
Hence, the base of the triangle is 34.5 mm.