Answer:
s = 45 m
Step-by-step explanation:
The velocity given in the question is uniform. Hence, the formula for the uniform velocity shall be used here. The formula is given as follows:

where,
s = distance traveled away from the brother = ?
v = constant speed = 3 m/s
t = time taken = (0.25 min)(60 s/1 min) = 15 s
Therefore, using these values in the formula we get:

s = 45 m