Slope-Intercept form of the equation of a line is the following:
Where "m" is the slope of the line and "b" is the y-intercept.
In this case you have this equation of the line written in Slope-Intercept form:
So you can identify that the slope and the y-intercept are the shown below:
When two lines are perpendicular, their slopes are opposite reciprocal. Knowing that in this case both lines are perpendicular and knowing the slope of one of them, you can determine that the slope of the other line is: