First, subtract #color(red)(80)# from each side of the inequality to isolate the #w# term while keeping the inequality balanced:
#80 - color(red)(80) - 2w >= 50 - color(red)(80)#
#0 - 2w >= -30#
#-2w >= -30#
Now, divide each side of the inequality by #color(blue)(-2)# to solve for #w# while keeping the inequality balanced. However, because we are multiplying or dividing an inequality by a negative term we must reverse the inequality condition:
#(-2w)/color(blue)(-2) color(red)(<=) (-30)/color(blue)(-2)#
#(color(blue)(cancel(color(black)(-2)))w)/cancel(color(blue)(-2)) color(red)(<=) 15#
#w <= 15#