All triangles have the same value, and all circles have the same value. What is the sum of three circles? \begin{align*} \Delta + \bigcirc + \Delta + \bigcirc + \Delta&= 21\\ \bigcirc + \Delta+\bigcirc+\Delta+\bigcirc &= 19\\ \bigcirc + \bigcirc + \bigcirc &= \ ? \end{align*}
