$$ \begin{align*} \textbf{Find the value of } \\&\ \left( 5 a-b\right)^2 + \left(b- 6 \right)^2 + \left( - 6 c - 5 \right)^2 = 0 \\&\ \left( 7 a-b\right)^2 + \left(b- 4 \right)^2 + \left( - 18 c - 5 \right)^2 = 0 \\&\ \left( 3 a-b\right)^2 + \left(b- 12 \right)^2 + \left( - 5 c - 5 \right)^2 = 0 \\&\ \text { where a, b and c are real numbers. } \\&\ \end{align*} $$