What is two thirds of a straight angle

A straight angle = 180 degrees

so 2/3 of a straight angle is 2/3 of 180..." of " means multiply
2/3(180) = 360/3 = 120 <==

You have 2 sides that are 2 cms and you have 6 sides that are 1/2 cm and you have 4 sides that are 1 cm. the smallest sides are 1/2 the medium sized sides are 1 and the smallest are 1/2. so to find the perimeter you have to add them all up together so your answer will be 11 cm's