noun
1
BAD : She had a difficulty in obtaining a visa.
GOOD : She had difficulty (in) obtaining a visa.
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have difficulty/difficulties (in) doing sth (NOT a difficulty ): 'Sometimes he has difficulty in making himself understood.'
2
BAD : I have great difficulty to understand him.
GOOD : I have great difficulty (in) understanding him.
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have difficulty/difficulties (in) doing sth (NOT to do ): 'You should have no difficulty in passing the exam.'