Answer:
X=-9
Step-by-step explanation:
Your proof is correct and very well done
This is an example of observational study, because the biologist is not interfering or interacting with the subjects of study but just watching and registering data (recording with cameras).
The biologist is not conducting an experiment because (he is not setting up special conditions to register different responses to drive conclusions), and the biologist is not making any survey (questionnaires for example).
Answer: observational study
72 + 74 is 146.
The angle sum of a triangle is 180.
180 - 146 is 34.
The answer is 586.17 cm^2