Those sitting the Edexcel C1 test say it was "harder than all the past papers" and didn't include as many whole numbers as was expected.
And a question on the amount of money given by "John's uncle" was cited by many, with some joking they'd need a rich relative to afford extra tutoring.
It comes a day after students vented their fury at the GCSE AQA Biology exam, which demanded students explain what an "independent business" was.
Pearson Edexcel said: "We can confirm that the paper was a reflection of the curriculum that students have studied this year.
"With every paper there there will always be questions that some students find difficult, which is often reflected in social media comment."