Answer:
7 m
Step-by-step explanation:
We see that the the side measuring 6 m corresponds to the side measuring 18 m. Also, the side measuring 8 m corresponds to the side measuring 24 m. In each case, the corresponding side of the right triangle is 3 times larger than the side of the left triangle. We divide 21 m by 3 to get 7 m.
Answer: 7 m
