Answer:
Option D) b + 34.8 = 54.6 is the equation can be used to find the value of b.
Explanation:
We are given the following information in the question:
Perimeter of scalene triangle = 54.6 cm
The sides of triangle given are b, a and 3a.
Thus, we can write that:

We are given that a = 8.7 cm
Putting this value, we have:

Thus, Option D) b + 34.8 = 54.6 is the equation can be used to find the value of b.