This is the 332nd most frequent Korean word.
보이는
"Visible" or "that can be seen."
In this sentence, '보이는' refers to the state of being visible or seeable, describing the condition of the painting.
그 그림은 멀리서도 잘 보이는구나.
That painting is clearly visible even from a distance.
'보이는' here modifies '문제들' (issues) to specify that they are the visible ones.
보이는 문제들 중에서 가장 중요한 것은 무엇인가요?
Among the visible issues, what is the most important one?
The word '보이는' is describing '사람' (person), indicating the person who appears or is visible in the photo.