x^2 - 3x + √5-x = √5-x + 18

Subtract √5-x from both sides: x^2 - 3x = 18. Rearrange into a quadratic equation: x^2 - 3x - 18 = 0. Factor the quadratic: (x-6)(x+3) = 0. The solutions are x=6 and x=-3.