Answer:
D
Step-by-step explanation:
The perimeter is 54.6.
a + 3a + b = 54.6. since a = 8.7,
8.7 + 3(8.7) + b = 54.6
8.7 + 26.1 + b = 54.6
34.8 + b = 54.6
b = 54.6 - 34.8
b = 19.8
They pretty much have the exact same examples in the instruction videos with different numbers; it helps to watch the videos again.
