HELP WITH MY PHYSICS HOMEWoRK?????

[k-k-k-kinsey :)]

i already did the problems, i just want to check if they're right. if they're wrong, do you think you could help me? you don't have to give me an answer or anything, a step-by-step explanation will suffice.

1. You have a spring with a 60 pound weight hanging from it. If the 60 pound weight stretches the spring 3 inches, how much will a 30 pound weight stretch the spring?
is it 1.5 inches? (my answer)

2. What is the spring constant (k) of the spring? Be sure to include the correct units of k.
is it 7,680? (my answer)

3. Two sound waves both of frequency 2 kHz interfere at a point. If their path length difference is PLD= 3.3 in, what type of interference do they go? Use v = 1100 ft/s for the waves' speed.
does it undergo destructive interference? (my answer)

FINALLY.....
what if the waves' frequency is 4 kHz?
does it undergo constructive interference? (my answer)