I'm brain dead for everything involved with math

Funny,

1. Your gonna plug in 1, 2, and 3, in the equation.

So, if you have y= 2x-1 you plug in 1 for x.
y=2(1)-1
y=2-1 which 2-1 = 1
That's how they got 1 under the y in the table.

So, lets plug in 2.
y=2(2)-1
y=4-1 which 4-1 = 3
3 goes under 1 in the y table.

Now, we plug in 3.
y=2(3)-1
y=6-1 which 6-1 = 5
5, goes under 3 in the y table.

It will be 3 next to 2 and 5 next to 3.