Answer:

Explanation:
We have been given the system of equations

Now, in order to solve the system of equation, we can use the below concept.
Since, both the equations, equation (1) and (2) is equal to the variable y. Hence, the expressions of the right hand side of both equations should be equal.
Therefore, we the rewrite it as

Therefore, b is the correct equation which we can use to solve the system of equation.