Well, y is decreasing by 60 miles per hour. So let me write it as negative 60 miles per hour. Now, similarly, let's say that this distance right over here is x. x is 0.6 miles right at this moment. So we know that x is equal to 0.6 miles. What is the rate at which x is changing with respect to time? Well, we know it's 30 miles per hour is how fast we're approaching the intersection. But x is decreasing by 30 miles every hour.