Haber process is used to prepare ammonia.
the balanced eq for it is:
N2+(3)H2 = (2)NH3
(the no. in bracket indicate mole number)
the ration is given 14:3
that means mol of Nitrogen are 0.5 and mol of Hydrogen are 1.5.
put these moles in that balanced equation you'll get 1 mol of NH3, which by mass is 17.
0.5 N2 + 1.5H2 = 1 NH3