Don L. answered • 03/20/15

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Don - Math/Science Tutor from Elementary School to College level

the set will be like this

here is a website that gives the simple idea of how to make a set

http://www.mathwords.com/s/set_builder_notation.htm

either one should be fine

## {1,2,3,...,123,124} = {x| x∈ Ν, 1≤x<125} where N is the natural number

## {5,10,15,20,25,30,35,40,45,50,55,60,65,70,75} = {5x| x∈ Ν and 1≤x≤15}

to find the boundary 1≤x≤15 for this part, it needs the min and the max number in the set, which is 5 and 75, respectively.

set the formula to get the x value (boundary)

5x = 5 so x = 1

5x = 75 so x = 15