if KNML is indeed a rectangle per se, then if that's true NK = ML, or namely 3y +21 = 5y + 11.
And likewise if it's indeed true, is also true that all interior angles it has are all 90°, or namely 2x - 10 = 90.
[tex]3y+21=5y+11\implies 21=2y+11\implies 10=2y\implies \cfrac{10}{2}=y\implies \boxed{5=y} \\\\\\ 2x-10=90\implies 2x=100\implies x=\cfrac{100}{2}\implies \boxed{x=50}[/tex]
