According to Markovnikov's rule, when hydrogen bromide adds to propene the major product is

Explanation

The hydrogen adds to the carbon that already carries more hydrogens, so the bromine ends up on the middle carbon. The underlying reason is that this route passes through the more stable secondary carbocation rather than a primary one, since alkyl groups release electron density and spread the positive charge. In the presence of peroxides the addition becomes a radical process and the anti Markovnikov product dominates instead.