What would be the waiting time if four clerks are working?

x(Number of clerks working) 6,8
y(Number of minutes wating time) 8,5

We have to points or ordered pairs (6,8)(8,5)

Before i use the slope intercept form i have to get the slope using the point slope form. y2 - y1 / x2 - x1 = m which ends up being -3/2.

Now when i plug the values in the slope intercept form y = mx + b. 8 = -3/2(6) + b --> 8 = -9 + b and solve for b. b = 17. Now it would be logically correct that the less clerks that work the more waiting time there will be. But is 17 minutes the right answer?