HMMT 2016 A10

Let $a, b$ and $c$ be positive real numbers such that

$$\begin{aligned} a^{2}+a b+b^{2} & =9 \\ b^{2}+b c+c^{2} & =52 \\ c^{2}+c a+a^{2} & =49 \end{aligned}$$

Compute the value of $\frac{49 b^{2}-33 b c+9 c^{2}}{a^{2}}$.