A skateboarder cannot be perfecting a trick while also riding a bicycle at the same time.
This justifies what answer for what question? Q & A:

Show your work and conclude with the exact phrasing "Therefore, the final answer is [answer]." where [answer] is just the final number or expression that solves the problem.
user
Premise: "A skateboarder is perfecting his trick on a wall."
Hypothesis: "A boy is riding a bicycle."
Do we know that the hypothesis entailed by the premise?
no