"difficulty to answer" is a correct and usable phrase in written English.
You would use it when describing a question or problem that is difficult to answer or solve. For example, "The students were stumped by the professor's questions, finding them too difficult to answer."
That is the question that her book, the first full-scale biography of Bruno in English, tries, with difficulty, to answer.
Patients completed the BSIqol in a median time <2 min. Only one patient reported some difficulty to answer the instrument.
For those questions volunteers like Tea and Alen had difficulty to answer, they would be referred to the team of doctors.
These criteria were necessary, considering that elderly people committed by these problems would face difficulties to answer the research questionnaires.
Money was borrowed from everyone and anyone to try and make ends meet, and eventually she stopped seeing her family because it was too painful to admit the extent of her difficulties and to answer questions about when they were going to get their money back.
Graham encounters severe difficulty when attempting to answer these questions.
While in the German sample, the mean percentage of symptomatic answers (pi) was 30% and 20 of the 58 items showed a percentage below 10% [ 19], in the Mexican sample the mean pi was 40% and only 3 items showed an extreme value for "difficulty to be answered with yes" with a pi below 10%.
The weakness of polytheism is especially revealed in the realm of questions about the ultimate origin of things, whereas monotheism runs into difficulties in trying to answer the question concerning the origin of evil in a universe under the government of one god.
All of these are potential measures of difficulty or complexity, but to answer the question in a comprehensible way, we have to pose the question in a way that can be analyzed.
In the upper class (wealthier) tracts, apart from the difficulties mentioned above, contact with the subjects was more complicated due to the inaccessibility of buildings and private neighbourhoods (even when not gated) and the difficulty to convince them to answer the questionnaire.
Furthermore, our results show that ∼50% of the Matched students agree with statements such as: "After I study a topic in biology and feel that I understand it, I have difficulty applying that information to answer questions on the same topic" and "When I am answering a biology question, I find it difficult to put what I know into my own words".
