Question

in an examination 3 candidates passed chemistry 29 passed physics and 3 failed both subjects. if 50 candidates sat for the examination, how many if them passed chemistry only

Answer 1

of the 50, 47 passed something
but you only list 3+29=32 as having passed something
Now, maybe you meant 30 passed chemistry. If so, then if x passed both, then
30+29-x = 47
x = 12
so, 30-12=18 passed only chemistry.