Start with the bottom equation and rearrange it so that it's a "y =" equation like so: 0 = 2x + 1 - y -> y = 2x + 1
now since you know "y" you may substitute that equation 2x + 1 into "y" of the first given equation to be: x^2 = (2x + 1) - 7 + 5x then simplify x^2 = 7x - 6 (I just put together like terms here to simplify the equation)
then you can make it to be: x^2 - 7x + 6 = 0 and there's your new and nice equation. now just solve for "x" using the quadratic formula or any other formula that you know
