Ok, so for the first equation, I would subtract y from both sides, thus resulting in:
x^2+5x-10=-y
And for the second equation, I would add y to both sides, thus resulting in:
x^2-x+3=y
Then we can get rid of the y variable in the systems of equations by combination both equations:
(x^2+5x-10) + (x^2 - x +3) is the same as -y+y.
So now you have:
2x^2-4x-7=0, and you'd have to solve this equation with the quadratic formula. I hope that helped.