Answer:
0.4
Step-by-step explanation:
Given
60 % wear neither ring nor a necklace
20 % wear a ring
30 % wear necklace
This question can be Solved by using Venn diagram
If one person is choosen randomly among the given student the probability that this student is wearing a ring or necklace is


The sum of probabilty is equal to 1 because it completes the set
Therefore the required probabilty is 0.4
A triangle always equals 180 degrees
Should be somewhere around there either way for 9. the angles are the same because you see the arrows on the parallel lines 8. I'm not quite as sure about
Step-by-step explanation:

Hence, 4th option is the correct answer.