12 less then 3 times the square of a number b is zero: 3b2-12=0;
Add 12 to each side of the equation: 3b2=12;
Divide each side of the equation by 3: b2=4;
Take the square root of each side of the equation, remembering that a perfect square has two square roots: b=√4, 2×2=4 and (-2)×(-2)=4, so the number b is 2 or negative 2.