1.) That just means that X will equal 8, so the same as:
3(8)-1
24-1
23
2.) The relationship is a function, there are no repeated elements in the domain(x column), and each domain is pair with one element in the range.
The function is y = 2x+1, when you double x and add 1, you get y.
3.) The relation is not a function for reasons I explained in 2.), x is paired with more than 1 element. The domain is 1,3,-5. Range is -2,2,0,4,-4