First, expand the terms within parenthesis by multiplying by the term outside the parenthesis - #color(red)(8)#:
#(color(red)(8) * (-3x)) + (color(red)(8) * (-4)) + 12 = 28#
#-24x - 32 + 12 = 28#
We can now add the constants on the left side of the equation:
#-24x - 20 = 28#
Next, we can isolate the #x# term on the left side of the equation by adding #color(blue)(20)# to each side of the equation which will also keep the equation balanced:
#-24x - 20 + color(blue)(20) = 28 + color(blue)(20)#
#-24x - 0 = 48#
#-24x = 48#
Now, we can solve for #x# by dividing each side of the equation by #color(green)(-24)# which will also keep the equation balanced:
#(-24x)/color(green)(-24) = 48/color(green)(-24)#
#(color(green)(cancel(color(black)(-24)))x)/cancel(color(green)(-24)) = -2#
#x = -2#
