H3C−CH2−C|CH3=CH2+HBr→A A (predominantly) is
CH3CH2−C|CH3H−CH2Br
CH3−CH−C|CH3H−CH3|Br
CH3−CH−C|CH3H−CH2−CH2Br
CH3−Br|C|CH3−CH2CH3
The reaction proceeds via the formation of the more stable carbocation. Hence, the major product!