To find the slope of the line that passes through the points \((3, 8)\) and \((-2, 13)\), we use the formula for the slope \(m\) given two points \((x_1, y_1)\) and \((x_2, y_2)\):
\[ m = \frac{y_2 - y_1}{x_2 - x_1} \]
Here, we can assign:
- \((x_1, y_1) = (3, 8)\)
- \((x_2, y_2) = (-2, 13)\)
Now, substitute the values into the formula:
\[ m = \frac{13 - 8}{-2 - 3} \]
Calculating the numerator and the denominator:
\[ m = \frac{5}{-5} \]
Simplifying this gives:
\[ m = -1 \]
Therefore, the slope of the line that passes through the points \((3, 8)\) and \((-2, 13)\) is \(\boxed{-1}\).