"Peter teaches Raj."
Translation:पीटर राज को पढ़ाता है ।
Generally you change the verb ending from -ना to -आना when you want to reverse the verb and make it something you're doing to someone else as opposed to doing it yourself. Study is पढ़ना, that's something that you can do, but when you want to do it to someone else, i.e make THEM study, it becomes पढ़ाना, to teach. The rule is not always the same though, each word can be a bit different. देखना = to see, दिखाना = to show. Another way to say teach is सिखाना, the reverse of सीखना. You'll come across this verb structure quite often, these are just a couple of examples, learn them as you go, the rule is not exact.