Straight-rights to the body are relatively easy punches to land - these punches are usually thrown from the outside so, stepping "in" while doing so is key - since the best way for your opponent to defend against a straight-right to the body is by them simply "stepping or pulling back", following up with a lunging left-hook to the head could be ideal - allow your forward-momentum from this hook to propel another right to the head - in the case they throw a retaliatory jab upon backing up, offer them a pullback-right hand to finish off the combo.