Help me I have inserted a picture of the question

I think this is correct

Explanation:

frequency definition is the number of complete waves produced per second so if you have 100Hz, it is 100 complete waves produced in 1 seconds, and when it says vibrates 300 times in 3 seconds, you find for 1 second

vibrations is most probably the frequency in one second

1 second 100 vibrations

thus the frequency = 100 Hz

hope this helps

close lines strong magnet less close weaker

if the person is shown to have +90n, then ans is -10n.

if the person is shown to have -90n, then ans is +10n.