#### Answer

$a) A'= \{x:x\geq{72.5}\}$
$b) B'= \{x:x\leq{52.5}\}$
$c) (A\cap{B})= \{x:52.5\lt{x}\lt{72.5}\}$
$d) (A\cup{B})= \{x:x\lt{72.5}, x\geq{72.5}\}$

#### Work Step by Step

a) A' refers to the set of elements that are not in A, which are all the numbers in the real set above 72.5.
b) B' refers to the set of elements that are not in B but in the real set, so the answer is any x less or equal to 52.2.
c) $A\cap{B}$ refers to the set of elements that are in A but at the same time are in B. So the answer is any number between 52.5 and 72.5.
d) $A\cup{B}$ refers to the union of the sets.