we will assume that the sticker is rectangular

let 'x' and 'y' represent the dimensions of the sticker and x,y>0

The perimeter of a red sticker is 18 millimeters:

2(x + y) = 18 divide both sides by 2

x + y = 9

y = 9 - x

The area is 8 square millimeters:

x*y = 8

plug y = 9 - x into the last equation:

x(9 - x) = 8

by solving we find:

x1 = 8 mm

x2 = 1 mm

click here to see the step by step solution of the equations

for x = 8 we have y = 9 - 8 = 1

for x = 1 we have y = 9 - 1 = 8 which is the same as the previous solution

the dimensions of the sticker are 1 mm and 8 mm.