The x-axis is the horizontal axis. A perfectly horizontal line that has no steepness at all. No slope. Or we could say that it has a slope of 0. A perfectly horizontal line goes through the y-axis at a specific point and never leaves that y value. x values can stretch from negative to positive infinity, but that y value remains the same because our line is horizontal. The y-intercept of our line is -7. Therefore, the place on the y axis the horizontal line goes through is at -7. So the equation for this line is y = -7.