Answer:
45
Explanation:
X+30=3x and then u just solve the equation.
One incident would definitely be during the cold war more specifically during The Bay Of Pigs
another would be during a false alarm in which we thought Russia had fired nuclear weapons at us and refrained from firing back before being sure
"To accommodate for lack of dependable rainfall" would be the best option as to why the ancient Chinese organized large groups of people to build and maintain irrigation systems, since when rainfall would not come for long periods of time, the crops would likely die without proper irrigation.