To tell if the equation 2y=8, first put the equation in y=mx+b form which is the formula for the linear equation. To do this, divide both sides by 2 and you get y=8 which is equivalent to y=0x+8, only there is a slope value of 0, meaning the graph is just a straight horizontal line. To graph this, you can plug in values, and when you do, notice that while the x values are changing, your y values remain the same which explains why the line is horizontal.