To solve the given linear equation, -9x - 9x = -9, begin by like-terms on the left side of the equation in order to begin isolating the variable x on on the left side as follows:
-9x - 9x = -9 (Given)
-18x = -9
Now, to finally isolate x on the left side of the equation and thus solve the given equation for the variable x, divide both sides of the equation by -18 as follows:
(-18x)/-18 = -9/-18
(-18/-18)x = -9/-18
(1)x = 1/2
x = 1/2
CHECK (ALWAYS PERFORM THIS STEP BACK IN THE ORIGINAL, GIVEN EQUATION!):
-9x - 9x = -9
-9(1/2) - 9(1/2) = -9
-9/2 - 9/2 = -9
-9/2 + (-9/2) = -9
(-9 + (-9))/2 = -9
-18/2 = -9
-9 = -9