Final answer:
Alexa's marriage to two brothers is considered polyandry, where one woman has multiple husbands, which differs from polygyny (one man, multiple wives) and is much less common worldwide.
Step-by-step explanation:
Alexa's marriage to two brothers is an example of polyandry, a form of marriage in which one woman is married to more than one man at the same time. Unlike polygyny, which is a marriage of one man to multiple women, and is the more common form of polygamy, polyandry is quite rare and only occurs in about 1 percent of the world's cultures. The practice of being married to more than one person at a time is generally considered socially and legally problematic in many places, and when someone is married to only one person at a time, it is termed monogamy. Bigamy, on the other hand, is the act of marrying one person while still legally married to another and is illegal in most jurisdictions.