First, divide each side of the equation by #color(red)(3)# to eliminate the constant while keeping the equation balanced"
#(3(4 - x)(2x + 1))/color(red)(3) = 0/color(red)(3)#
#(color(red)(cancel(color(black)(3)))(4 - x)(2x + 1))/cancel(color(red)(3)) = 0#
#(4 - x)(2x + 1) = 0#
Solve each term on the left side of the equation for #0#:
Solution 1)
#4 - x = 0#
#-color(red)(4) + 4 - x = -color(red)(4) + 0#
#0 - x = -4#
#-x = -4#
#color(red)(-1) xx -x = color(red)(-1) xx -4#
#x = 4#
Solution 2)
#2x + 1 = 0#
#2x + 1 - color(red)(1) = 0 - color(red)(1)#
#2x + 0 = -1#
#2x = -1#
#(2x)/color(red)(2) = -1/color(red)(2)#
#(color(red)(cancel(color(black)(2)))x)/cancel(color(red)(2)) = -1/2#
#x = -1/2#
The solutions are: #x = 4# and #x = -1/2#