Question 355361
Let x be the number. You are told
{{{(x*x) - (x+x) = 99}}}
{{{x^2 - 2x = 99}}}
{{{x^2 -2x - 99 = 0}}}
{{{(x-11)(x+9) = 0}}}
So either {{{x-11 =0}}} or {{{x+9 = 0}}}
Thus x is either 11 or -9

Check your answers.
Is 11^2 - 22 = 99??  
is 121-22 = 99 ??
Is (-9)^2 - (-18) = 99
Does 81 + 18 = 99??