Answer:
51/8 or 6 3/8 (depending on if you need to simplify or not)
Explanation:
Since the girl is 4.25 feet tall, you would multiply that by 1.5 which would get you 6.375 then, you convert to a fraction. The fraction would be 51/8 which would be equivalent to 6 3/8. So, Jebb is 6 3/8 feet tall.
Hope this helped! :)