I am not too sure if my answers are correct. Here are the questions:

1. A student standing near a brick wall claps her hands and hears the echo 0.250 s later. If the speed of sound was 340.0 m/s, how far from the wall was she?

For this question I got 85 m.

2. How much faster does sound travel on a hot summer day, 40 degrees celsius than on the coldest day, -40 degrees celsius?

For this question, I got 48.5 m/s (I found the speed of air for each temperature. then I subtracted the speed of air from summer from the one from winter and got 48.5 m/s)

3 answers

so 1 second would be 340m, 1/4 second is 1/4*340 or 85meters
correct!!!!:)

355m/s-306m/s =49m/s

correct !
thanks again!
For the questions of echo we take
2d = v•t
So the answer of the first question must be
d = (340)(0.25)/2
d = 42.5 m