HBr when reacts alone(with alkene) then it follows Markonikov's rule (while breaking double bond) i.e. Br will get attached to the most stable C atom(by breaking the double bond). But here since peroxide is present it will follow Anti Markonikov's rule and Br will not get attached to stable location.
If Propene could had reacted with HBr only, it will form 2-Bromopropane.
And if it is reacted in presence of peroxide it will form N Propyl bromide (or 1-Bromopropane)