Explanation:
Answer: 19, because all you´re doing for mark is dividing his actual height from the profile picture.
Marks sister: 66.5, because you will take her height (3.5) and you will put x over 3.5 in fraction form. Then you will take marks profile picture height, and put it in fraction form (76 over 4) then you will cross multiply 3.5 and 76 which will give you 266. Then you´ll divide 266 by 4 which would give you 66.5