1. The problem statement, all variables and given/known data The weight of rod AB is 4[N] and that of piece D is 10[N]. the moment at joint C is 1.8[Nxm]. what is the weight of rod AC. 2. Relevant equations Moments: ##M=F\cdot L## 3. The attempt at a solution Rod AB doesn't contribute to the moment at C: $$10\cdot 15+180=W_AC\cdot 5\rightarrow W_AC=66[N]$$ It's 6[N] in the book.