A ratio of the number of items within a defined unit of area measures

Density

Step-by-step explanation:

Density is the number of items per unit area. It is gotten by dividing the number of items by the area it occupies. It measures the compactness of an item in a given area. The higher the density, the more compact items are per unit area and the lesser the density, the less compact items are per unit area. It is measured in items/m²

18

step-by-step explanation:

draw the shape and you will see that f and k are actually at adjacent vertices (points of the hexagon that are neighboring).   so find the distance between (1,2) and (4,2).   that is easy since (1,2) and (4,2) is just a vertical distance to count, which is 3.   it is a regular polygon which means all sides are congruent.   you have 6 sides (hexa) so multiply 6 by 3 to receive 18.

-2x + 7 = 7

subtract 7 from both sides.

-2x = 0

divide both sides by -2.

x = 0