What do you call it when somebody spends 20 years in the 24th row of a theater page 222?

"living in exile"

This is referred to as living in exile, because the 24th row is the "x-aisle", which is a play on the word "exile" because that's what it sounds like out loud. Typically, this is used as a joke or a pun in algebra or another math class.

16.

Explanation:

As per the question,

Number of words to be memorized = 20

Portion he has done = 4/5

No. Of words he has memorized so far = 20 * 4/5 = 16 words.

Thus, the no. of words that Ivan has memorized till now would be sixteen(16) as out of the total(five-fifths) which means five portions of four words each, Ivan has learned four of them that means 4*4 = 16. Therefore, 16(sixteen) is the answer.