What is a shape that is 14cm in perimeter and area of 12cm?

Area is measured in square centimetres so there cannot be any shape with an area of 12 cm.

Area = length 3.464102 x width 3.464102 = 12.000001cm2

Perimeter = 3.464102 x 4 = 13.856408 (approximately 14cm)

The shape is a square.