jmc

For simplicity, suppose $\Delta =a$, $♢=b$ and $\bullet =c$. Then, $$3a+b=9c$$ $$a=b+c$$ and we want to know what $2b$ is in terms of $c$. Substituting the second equation into the first, we have $$4b=6c\Rightarrow 2b=3c$$ Thus, we need $3$ $\bullet$'s $\to \boxed{3}$.