A 80.0 kg girl lowers herself to the ground from a height of 11.6 m by holding onto a rope running over a pulley to a 56.0 kg sandbag. What is the magnitude of the acceleration of the girl?
A simple web search reveals many such examples. The sparknotes site has a particularly lucid write-up.
The end result, describing the acceleration of two unequal masses m and M is
a = g(M-m)/(M+m)