Find x for the equilateral triangle R S T if R S = x + 9, S T = 2 x, and R T = 3 x - 9.
Choices:
A:3
B:6
C:9
D:12
Please directly answer the question and provide the correct option letter, e.g., A, B, C, D.
Question: Find x for the equilateral triangle R S T if R S = x + 9, S T = 2 x, and R T = 3 x - 9.
Choices:
A:3
B:6
C:9
D:12
Please first conduct reasoning, and then answer the question and provide the correct option letter, e.g., A, B, C, D, at the end.
Question: Find x for the equilateral triangle R S T if R S = x + 9, S T = 2 x, and R T = 3 x - 9.
Choices:
A:3
B:6
C:9
D:12