How do i know which one is complementary?

Complementary angles are 90 degrees
Supplementary angles are 180 degrees.

you add two angles and they have to equal either 90 or 180 in order to be complementary or supplementary.

the answer is B because <SXT is 25 and <TXU is 65. when you add those two, the answer is 90.

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