PreCal
posted by Hannah .
Perform the addition or subtraction and use the fundamental identities to simplify.
tan x  sec^2 x / tan x
I do not know where to start.

The way you typed it ....
tan x  sec^2 x / tan x
= tanx  (1/cos^2x)(c0sx/sinx+
= tanx  1/(sinxcosx)
= tanx  cscxsecx 
Hannah,
if you continue by substituting sin and cos for the tan,csc and sec functions, you can simplify further. This will be left as an exercise for yourself.