Substitution is the only way to solve this because you have different powers of x
You can solve that quadratic to give two values of x:
Using those two values of x plug into equation 1 to find their corresponding y values (you will get two pairs of solutions as a final answer)
edit: an example
you know that x = 3 is one of the roots and so you can sub x=3 into eq1 to find y:
Hence is one pair of solutions. Can you do the same thing for the other root?