Answer:

Step-by-step explanation:
Consider the real number y such that f ⁻¹(x) = y

We need to find y in order to determine the expression of f ⁻¹(x)
f(y) = x ⇔ -2y + 4 = x
⇔ 4 - x = 2y
⇔ y = (4 - x)/2

In math, the irrational numbers are all the real numbers which are not rational numbers, the latter being the numbers constructed from ratios of integers.
The answer is B