Evaluate: 
27.63² - 22.37²

If xy + 1 = y² and
z= (1/x) - (1/xy),
express z in terms of y

If y is a positive number, for what values of y is
4 + 3y < 10 ?

The marks scored by students in a test are recorded in the table below

Calculate semi interquartile range

The probability of obtaining a prime number in a single toss of fair die is

The universal set U contains all integers.
Subsets of U are defined as
P = {x : x ≤ 3}
Q = {x : -5 < x < 12}
R = {x : -2 ≤ x < 5}
Q ∪ R = ?