How to show your work to solve  3r^2-16r-7=5

OK so   3r^2-16r-7=5 Subtract five from both sides 3r^2-16r-7-5=0 Add like terms 3r^2-16r-12=0 Factorise it, this means putting it into brackets (3r + 2)(r - 6) Find out what multiplies to make negative twelve but adds to make negative sixteen However none of the terms do this so we put negatives next to the "r"s (-3r + 2)(-1r - 6) The answer is r=6