The x-intercept is an ordered pair of the form (a,0), where a is the value of x when y = 0. It is called the x-intercept because this ordered pair describes the point where the line represented by your equation crosses (or 'intercepts') the x-axis.
So, all you need to do is substitute 0 for y in your equation and then solve the result for x.
By the way, finding a y-intercept, i.e. the point (0,b), is just the opposite process, that is substitute 0 for x in your equation.
