A. How did the Greek city-states respond to the Persian invasions? Why is
the Greek victory over Persia considered so remarkable?

Explanation:

Following the two Persian invasions of Greece, and during the Greek counterattacks that commenced after the Battles of Plataea and Mycale, Athens enrolled all island and some mainland city-states into an alliance, called the Delian League, the purpose of which was to pursue conflict with the Persian Empire, prepare for future invasions, and organize a means of dividing the spoils of war. The Spartans, although they had taken part in the war, withdrew from the Delian League early on, believing that the war’s initial purpose had been met with the liberation of mainland Greece and the Greek cities of Asia Minor. Historians also speculate that Sparta decided to leave the League for pragmatic reasons, remaining unconvinced that it was possible to secure long-term security for Greeks residing in Asia Minor, and as a result of their unease with Athenian efforts to increase their power. Once Sparta withdrew from the Delian League after the Persian Wars, it reformed the Peloponnesian League, which had originally been formed in the 6th century and provided the blueprint for what was now the Delian League. The Spartan withdrawal from the League had the effect, however, of allowing Athens to establish unchallenged naval and commercial power, unrivaled throughout the Hellenic world. In fact, shortly after the League’s inception, Athens began to use the League’s navy for its own purposes, which frequently led it into conflict with other, less powerful League members.

for this case we have the following equation:

we apply distributive property to the terms within parentheses.

subtracting 2 on both sides of the equation:

d definitly is not