18x - 30 (perimter) = 6x (6 times one length because 6 sides in a hexagon)
18x = 6x + 30 (taking 30 to the other side)
12x = 30 (taking 6x to the other side to isolate the x)
x = 2.5 (dividing 30 by 12 to find value of x, or value of one length)
We know each length is 2.5 because if you do 18*2.5 - 30, you get 15 units. Also, if you do 6 * 2.5, you get 15 units, so it's correct.