Question 7176
You can start by preparing an input/output table for each equation.
The purpose of this input/output table is to give you the coordinates of a number of points which you can then place on you graph paper in the appropriate places.  This will allow you to draw the line through these points to get the graph of the equation.

I'll do 1. and 4. then you will be able to see how to do the others.

1. y = 2x  Remember that x is the independent variable. This means that you can assign any value you want to x and the resulting value of y (the dependent varable) depends on what value you have assigned to x. 
Make a table of the values that you assign to x (input) and the resulting values of y (output).

{{{y = 2x}}}
 x......y
 0......0
 1......2
 -1....-2 

Now let's see what the graph of this looks like.

{{{graph(300,200,-8,8,-8,8,2x)}}}

4. {{{y = x^2-4}}}

x.....y
0....-4
1....-3
2....0
-1...-3
-2...0

Let's see what the graph of this one looks like:

{{{graph(300,200,-8,8,-8,8,(x^2-4))}}}

See if you can do the others.