First, expand the terms in parenthesis by multiplying each term within the parenthesis by the term outside the parenthesis:
#color(red)(-1/3)(9x + 18) - 2x = -66#
#(color(red)(-1/3) xx 9x) + (color(red)(-1/3) xx 18) - 2x = -66#
#(color(red)(-9/3)x) + (color(red)(-18/3)) - 2x = -66#
#-3x + (-6) - 2x = -66#
#-3x - 6 - 2x = -66#
Next, group and combine like terms on the left side of the equation:
#-3x - 2x - 6 = -66#
#(-3 - 2)x - 6 = -66#
#-5x - 6 = -66#
Then, add #color(red)(6)# to each side of the equation to isolate the #x# term while keeping the equation balanced:
#-5x - 6 + color(red)(6) = -66 + color(red)(6)#
#-5x - 0 = -60#
#-5x = -60#
Now, divide each side of the equation by #color(red)(-5)# to solve for #x# while keeping the equation balanced:
#(-5x)/color(red)(-5) = (-60)/color(red)(-5)#
#(color(red)(cancel(color(black)(-5)))x)/cancel(color(red)(-5)) = 12#
#x = 12#