In a class of 100 students 40 students study both maths and science 5 students do not study maths nor science.Twice as many students that study science study maths

A.how many students study science
B.how many students study maths
C.how many students study only one subject

If m students study only math, and 2(m+40) study science.

So, now we have
m + 2(m+40) = 100-5
m = 5
(B) 45
(A) 90
(C) 5+50 = 55