ANSWER
Step-by-step explanation
H(x) represents the percent of US households with internet use x years after 1980.
What this function already tells us is that in this function, the percentage of US households with internet use is dependent on the number years after 1980.
Therefore, H(23) = 55 would mean that:
x = 23
Therefore, 23 years after 1980 (2003), 55% of US households use the internet.
In otherwords, 55% of US households have internet us