Andrew's three symmetric numbers

Algebra Level 3

Andrew was playing with three numbers $a,b$ and $c$ .
First, he subtracted $b$ from the sum of other two and got 1,
then he subtracted $c$ from the sum of other two and got 2,
then he subtracted $a$ from the sum of other two and got 3.

Then, Andrew challenged his friends to find the value of $\dfrac{b+c}{a}$ . So what is the value of $\dfrac{b+c}{a}$ ?