A + B = C
D - C = A
E - B = C

Based on the above equations, can you find out the outcome for:
D + F ?

In this question, the alphabets represent their equivalent numeric position.
A = 1, B = 2, C = 3 and so on.
Thus,
A + B = c
=> 1 + 2 = 3

D - C = A
=> 4 - 3 = 1

E - B = C
=> 5 - 2 = 3

Which is why,
D + F = 4 + 6 = 10
Since, J is the 10th alphabet,
D + F = J.