Answer:
b = 69/2 mm
Explanation:
Let h: height of triangle
Let b: base length
Writing the height in terms of the base length: h = 2b + 5 mm
We equate that to the given height: 74 mm = h = 2b + 5 mm.
Solving this for b, we subtract 5 mm from both sides, obtaining
69 mm = 2b.
Then b = 69/2 mm