Answer:
18
Step-by-step explanation:
Mark is 18 years old.
This is the concept of transformations, given that ABC was rotated it implies that it retained it's original dimensions. This means that ABC is proportional to EFD. Therefore, given that EF=4.2 cm, DF=3.6 cm and DE=4.5 cm. The CB=FD=3.6 cm
Since you are going in feet first calculate10 yards into feet and then 168 inches into feet. Then subtract the two. Hope that helped :)