Use factorisation to solve this. You must find a pair of numbers that add to make 6 and multiply to make 5. In this question, 5 and 1 add to make 6 and they also multiply to make 5. So the factorised equation here is (x+5)(x+1)=0. By setting each bracket to be 0, we can see that x can be equal to -5 (when (x=1)=0, x+5=0 so x=-5) or -1 (when (x=5)=0, x+1=0 so x=-1)