The perimeter of the scalene triangle is 54.6 cm.
*pretend this is the triangle
3a, a b

Which equation can be used to find the value of b if side a measures 8.7 cm?
A. 8.7 + b = 64.6
B. 17.4 + b = 54.6
C. 21.6 + b = 54.6
D, 34.8 + b =54.6