Question 184870
Let the number be n, so...
{{{n^2-n = 12}}} Subtract 12 from both sides.
{{{n^2-n-12 = 0}}} Factor this quadratic equation.
{{{(n+3)(n-4) = 0}}} Apply the zero product rule.
{{{n+3 = 0}}} or {{{n-4 = 0}}} therefore:
{{{n = -3}}} or {{{n = 4}}} 
Check:
{{{(-3)^2-(-3) = 12}}}
{{{9+3 = 12}}}
{{{12 = 12}}} OK!
{{{4^2-4 = 12}}}
{{{16-4 = 12}}}
{{{12 = 12}}} OK!