From the first and fifth statement, I have filled in the above numbers.
The second statement gives: d + e + f + 4 = 48
The third statement gives two different equations: d = 2 e and d = 4 (4) = 16
The fourth statement gives: a + b + d + 4 = 124
The sixth statement gives: d = 4 + b
Remember that the total number of students is 208