Check the picture below.
let's now recall that the sum of all interior angles in a triangle is 180°.
[tex]\bf \stackrel{\measuredangle E}{(188-14x)}+\stackrel{\measuredangle C}{(-5+8x)}+\stackrel{\measuredangle D}{(51)} = 180 \implies 188+51-5-14x+8x=180 \\\\\\ 234-6x=180\implies -6x=-54\implies x=\cfrac{-54}{-6}\implies x=9 \\\\[-0.35em] ~\dotfill\\\\ \stackrel{\measuredangle NED}{14x-8}\implies 14(9)-8\implies 126-8\implies \stackrel{\measuredangle NED}{118}[/tex]
