Answer:
54
Explanation:
you have to use the principal of BODMAS
12 + 23 x 2 + 3 - 7
12 + 46 + 3 - 7
61 - 7
54
Natural environment has the ability to gather some pollutants yet if too much then the environment could no longer handle it. A leaky sewage can pollute an aquifer with I. arsenic as the contaminant. Arsenic is a metalloid existing in the Earth's crush. Exposure is natural yet can be aggravated by the human activities.
Answer: The hypothesis would become a theory.
The Development of the Middle Class and Working Class.