The perimeter of the scalene triangle is 54.6 cm.

Which equation can be used to find the value of b if side a measures 8.7 cm?

8.7 + b = 54.6

17.4 + b = 54.6

26.1 + b = 54.6

34.8 + b = 54.6

Are you sure it's a scalene triangle because if you only know one side and all the other sides are different lengths then it's impossible to computer unless we know angle measures. It would have to be isoceles or we would need angle measures