(X-5)(X-6)
First you look at the last number and find multiple of 30 that also add/subtract to get 11.
In this case 5 and 6 both “add up” to 11 and multiply to get 30.
BUT since you’re looking for a negative 11 you can’t add positive 5 and 6 so that is why you add together negative 5 and 6.
And in multiplication rules two negatives make a positive.
