Arrange in the order of increasing basicity  $({\mathrm{NO}}_2,$${\mathrm{K}}_2\mathrm{O},\mathrm{ZnO})$ :

Due to its position on the right side of the periodic table, nitrogen is a non-metal and produces acidic oxides. This oxide will thus have the least basicity. While transition metals like zinc are in the centre and will produce a less basic oxide, potassium is on the far left and will produce a more basic oxide.
In light of the element's location in the periodic table and the oxide's basicity order's metallic properties,

${\mathrm{NO}}_2<\mathrm{ZnO}<{\mathrm{K}}_2\mathrm{O}$