First, subtract #color(red)(5)# from each side of the inequality to isolate the #u# term while keeping the inequality balanced:
#-3 - color(red)(5) >= -4/7u + 5 - color(red)(5)#
#-8 >= -4/7u + 0#
#-8 >= -4/7u#
Now, multiply each side of the inequality by #-color(blue)(7)/color(green)(4)# to solve for #u# while keeping the inequality balanced. However, because we are multiply or dividing an inequality by a negative number we must reverse the inequality operator:
#color(blue)(-7)/color(green)(4) xx -8 color(red)(<=) -color(blue)(7)/color(green)(4) xx -4/7u#
#56/4 color(red)(<=) -cancel(color(blue)(7))/cancel(color(green)(4)) xx -color(green)(cancel(color(black)(4)))/color(blue)(cancel(color(black)(7)))u#
#14 color(red)(<=) u#
To state the solution in terms of #x# we can reverse or "flip" the entire inequality:
#u >= 14#