If I remember correctly, at least two of the questions so far–including the hated May 33rd question–have come from a single reference source. Since these guys seem to be far more interested in prolonging the agony than researching decent questions, that source would be the first place I would look.
Unfortunately, I cannot remember what that source is.
I had that thought too - I believe the current rate for federal jury duty is $40/day. Also, I believe the current witness fee is $40.
If I have the time, I will look up what it was in the past, and when it became $40.
(It seems unlikely that it was $2.75/hr anytime before the 1940s, though. hmmmm . .)
The People’s Almanac.
I’ll check the three volumes out, but I doubt it’s in there.
Given the specificity of “77 years,” my guess is that it’s some profession that started in 1924.
FWIW, my Mom made $25 a week in 1940 as a (pre-war) secretary in NYC - the implication being that whatever paid $2.75/hour in 1923 was pretty rockin’ work.
The question is, “What job salary has gone from $2.75 per hr to $40.00 in 77 years?” It looks like it’s asking for a “job salary,” not an actual job title. Is this just a math problem? If so, my answer is $24,088.075. Ah, I was never good at math. 
Is there anywhere that we can actually hear how the question is asked? People seem to think the phrasing is important, so it may help to hear the question spoken.
I think focusing on the salary alone might not be enough. One possibility is that even after inflation is accounted for, the job still essentially pays the same, but the person works less time per week doing it. Therefore the amount of compensation per hour actually goes up over time. This may not be a regular 9 to 5 job that they are talking about here.
I thought of this possibility when I saw the odd phrasing of the question in the OP.
This phrasing of the OP also leads me to thinking that it may not necessarily be a 20th century job salary. The question doesn’t specify which 77 years, or which century those 77 years are primarily located.
OneChance and Atreyu may be on to something. Another thing to keep in mind is that the length of the work week has changed over the years as well.
Again, the original question was “What job salary has gone from $2.75 per hr to $40.00 in 77 years?” The use of the present perfect (has gone) instead of the simple past (went) suggests that the time frame is from the present to 77 years in the past. In other words, it is not asking about just any period of 77 years in the past, but the specific period of 1924 to 2001. (Unless they got the grammar wrong.)