So we want to know what do we need to measure to determine the wavelength of the wave on the image. A wavelength is the distance between peaks of the wave. More generally, the distance on which the wave shape repeats. So on the image we need to measure X to determine the wavelength. So the correct answer is X.
A. sandwiches per hours is 4.5/hour
b. hours per sandwich is 0.33/sandwich
The blank is -8 because -6 +-8=-14+-3=-17.
