1. Draw a picture.  Label the hypotenuse y and the horizontal leg x.  The vertical leg is always 12.
2. State an equation involving x and y that is always true, using the Pythagorean Theorem.
3. Differentiate the equation with respect to t.
4. Solve the equation for dy/dt.
5. Find the values of y and dx/dt when x = 5.
6. Substitute these values into the equation to find dy/dt.