Now we need to know what velocity to use. The velocity of sound in air is not appropriate, since the sound wave is vibrating in a string, not in air. Then we know everything, and we can get frequencies. So that looks good. This was pretty simple to figure out if you remember what we did in discussion.
L is different.
We want to know wavelengths. We know the number of nodes and the length, so we know how many wavelengths are in each length. We can divide these two to get the length of one wavelength. So count up the number of wavelengths in each picture and divide L by that. B. FG are the same, AE are the same.