Note the equal sign. What you do to one side, you do to the other.
Follow PEMDAS.
First, distribute -3 to all terms within the parenthesis.
-9 = -3(x + 2)
-9 = -3x - 6
Next, do the opposite of PEMDAS. Isolate the x. Note the equal sign. What you do to one side, you do the other.
Add 6 to both sides
-9 = -3x - 6
-9 (+6) = -3x - 6 (+6)
-9 + 6 = -3x
-3x = -3
Isolate the x. Divide - 3 from both sides
-3x/-3 = -3/-3
x = -3/-3
x = 1
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1 is your answer for x
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hope this helps