`3x-2-7,3/2x+9=1/2, y/3+(y-2)/4=5` are linear equations in one variable, because the highest power of the variable in each equation in one whereas the equations `3x^2-2x+1=0, y^2-1=8` are not linear equations, because the highest power of the variable in each equation is not one. In this chapter, we shall study linear equations in one variable only.