Question

In an examination a candidate has to pass in each of the four subjects in how many ways can he fail

Answer 1

No. of ways he can pass or fail in examination = 2⁴ = 16
To pass, one has to pass in all the subjects = 1 way.
so no. of ways in which he can fail = 16 - 1 = 15

Answer 2

if dad has to pass in examination