The solution is where the curves intersect.
So the solution exists at the point where the x's are equal, but also where the y's are equal.
So we can set our y's equal to one another.
[tex]\rm y=x^2+1\qquad\qquad\qquad y=3x+2[/tex]
We call this method substitution,
[tex]\rm x^2+1=3x+2[/tex]