Premise: "A young man in a blue t-shirt walks past an alley while talking on his cellphone."\nHypothesis: "A man is talking on the phone while walking."\nDo we know that the hypothesis entailed by the premise?
Let's think step by step below.
yes
A man walks past an alley while talking on his cellphone implies talking on the phone while walking.

.

So, the final answer is yes