Physics
posted by Sarah .
A ladder of weight 200 N and length 10 m leans against a smooth wall with no friction. A firefighter of weight 600 N climbs a distance x up the ladder (x goes from the bottom of the ladder to the firefighterâ€™s feet). The coefficient of friction between the ladder and the floor is 0.5. What is the highest value of x if the ladder is not to slip?

tycho.physics.wisc.edu/courses/phys201/spring08/Lectures/Solids.pdf
see that solution. I can't help you without a diagrame presented there. 
10m