x = 2 , 4 , 6 , 8

y = 18, 34, 50, 66

This is supposed to be a table where the x lines up with the y in order

How would I find the equation to solve this when x = 20?

x goes up by +2
y goes up by +16 but starts with 18

I already posted this and got the answer: y = 2 + 8 x

But I want to know, how you come up with the equation?

Where did the 8 and 2 come from?