<span>In Babylonia, tunnels were used extensively for irrigation; and a brick-lined pedestrian passage some 3,000 feet (900 meters) long was built about 2180 to 2160 BC under the Euphrates River to connect the royal palace with the temple. Hopefully this answer helps
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Problem 11) Start with set U = {1,2,3,4,5} and cross off 1,2,3 to be left with A' = {4,5}. We basically erase everything found in set A. You have the correct answer. Nice job.
Problem 12) Start with U = {1,2,3,4,5} and erase '5' to be left with {1,2,3,4}. So B' = {1,2,3,4}. You are correct here as well.
I can't help with the other problems since either letters, numbers or symbols are missing. Please make a new post and provide those updates.
I am assuming this is a triangle.....P = a + b + c
P = 2a - 3 + 2a + 3a + 1....combine like terms
P = 7a - 2 <==
