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