The mean would be 58!! Basically what you’re doing to get the mean is adding all of the numbers together and dividing by how many you’re adding. In this case, you would add all of the numbers and divide by 8 because you have 8 numbers ! :D
Try googling this it will give you some examples and definitions.
https://mathbitsnotebook.com/Geometry/SegmentsAnglesTriangles/SATTriangleTypes.html
If 40% of the cameras are digital, that means 60% of them are not digital.
If 60% of all cameras is 24, then 20% is 8, making 40% 16 cameras.