Derivation of quotient:
`(f/g)'=(f' cdot g-f cdot g')/(g^2)` (1)
`(sec x)'=(1/cos x)'=sin x/(cos^2 x)=secx tanx` (2)
Also as you probably know `x'=1`.
Now by using rule for derivation of quotient (1) and knowing how to derivate `sec x` (2) we get
`(sec x/x)'=(sec x tan x cdot x-sec x)/(x^2)` <-- Solution