Verified answer

x^2 - 5x - 4x + 20 - 2 = 0

x^2 - 9x + 18 = 0

x^2 - 3x - 6x + 18 = 0

x(x - 3) - 6(x - 3) = 0

(x - 6)(x - 3) = 0

x - 6 = 0 or x - 3 = 0

x = 6 or x = 3

First, distribute (multiply out the left hand side

(x - 4) (x - 5)

= x^2 -9x + 20

so

x^2 - 9x + 20 = 2

Now bring everything to one side (add -2 to both sides)

x^2 - 9x + 18 = 0

Factor

(x - 3)(x - 6) = 0

so either x = 3 or x = 6

x^2 - 9x + 20 = 2

x^2 - 9x + 18 = 0

(x - 6)(x - 3) = 0

x = 6 or x = 3

x^2 - 9x + 20 = 2

x^2 - 9x +18 = 0

(x - 6)(x - 3) = 0

x = 6 or 3