1. The problem statement, all variables and given/known data 2. Relevant equations M = 3(L – 1) – 2J L= number of links, J = number of joints 3. The attempt at a solution As far as I can see, using the above L and J values for each linkage yields the correct M value. However, the L and J values lead me to think I'm missing something. Can someone explain why L = 4 for the first and second linkages? In the first one there are only 3 links and in the second linkage there are only 2 links. Also, surely for the second one J = 3 since there are only 3 visible joints? Similarly, why does L = 5 for the bottom left linkage when there are only 4 links and why does L = 4 and J = 3 for the bottom right linkage when there are only 2 links and only 2 joints?