A fair die is tossed repeatedly until a six is obtained. Let X denote the number of tosses required and let a=P(X=3), b=P(X ≥ 3) and c=P(X ≥ 6 ∣…

A fair die is tossed repeatedly until a six is obtained. Let $\displaystyle X$ denote the number of tosses required and let $\displaystyle a=P(X=3), b=P(X \geqslant 3)$ and $\displaystyle c=P(X \geqslant 6 \mid X>3)$. Then $\displaystyle \frac{b+c}{a}$ is equal to $\displaystyle \_\_\_\_$.