Question 259061
Very poorly worded question.
We do not know what is meant by the 13 who said both. We don't know if they were included in those who said they took physics and chemistry.
We don't know what how many were surveyed who answered none or answered biology or another science.
We therefore need to assume that the 13 were included in the others and there were no other responses and all the students surveyed are included in these 
numbers.

So as not count the 13 twice we add the two and subtract 13
47+28=75-13=62 surveyed