I assume you learnt some differentiation.
Use the quotient rule:
when y = u/v
dy/dx = [v(du/dx) - u (dv/dx)] / v²
In your case y= (x+3)/(x-2) so
dy/dx = [(x-2)1 - (x+3)1] / (x-2)²
= (x-2-x-3)/ (x-2)²
= -5 / (x-2)²
I like to keep it in brackets, but you can expand if needed.