Explanation:
From Statement I
Let the total number of student be X
Let the male students be A and female students be B.
It is given that,
A-B = 3
and A + B = x
Weight of total students = 61.08 × x
Weight of male students = 63 × A
Weight of female students = 59 × B
∴ 61.08(3+2B) = 63(3+B) + 59B
183.24+122.16B=189+63B+59B
0.16B=5.76
B=36
∴ A=39
∴ Total number of students = 36+39=75