3(x-2)(x+6)-5(x-2)(x-3)

(x-2)(3(x+6)-5(x-3))

(x-2)(3x+18-5x+15)
(x-2)(-2x+33)
-2x^2+37x-66

or

3(x^2+4x-12)-5(x^2-5x+6)
3x^2+12x-36 -5x^2+25x-30
-2x^2+37x-66