Edge detection greyscale help

New to imagej
How to calculate the difference in grey levels between adjacent pixels on imagej using 1 image which is all just grey and another which is in RGB scale of a circuit.


You need to provide more details of exactly what you want.
You can get the greyscale values of a pixel in an image by placing the mouse cursor on the desired pixel and looking the reported value in the info region (bottom of the IJ window).
But it is unclear what you are really after. E.g. how do you determine the pixels you want to inspect?

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It’s now been edited

Is this some kind of homework?

From the url in the image you posted and now erased, it seems that this is a homework/task from an online course at Nottingham Trent University.
Please do your own homework.