The figures shown are similar. What is the scale factor? A. 1/9 B. 3/7 C. 4/7 D. 6/7

Answer:
C. 4/7
Step-by-step explanation:
The scale factor is the ratio of corresponding side lengths (the only ones marked with a length).
... 12/21 = 4·3/(7·3) = 4/7