We need the equation in the form (x+a)(x+b)=0. The numbers in the brackets (a and b) must multiply together to get the constant at the end of the equation, in this case 12. The numbers (a and b) must add together to give the x coefficient, in this case 7. The values that satisfy both these conditions are 3 and 4. So we have (x+3)(x+4)=0In turn put each bracket equal to 0 and rearrange for x.(x+3)=0 x=-3(x+4)=0 x=-4