"Answer this question."
Translation:इस सवाल का जवाब दो।
If you replace सवाल by प्रश्न or जवाब by उत्तर, the sentence would still be correct. However, as with many other 'तत्सम' words (words picked as is from Sanskrit into Hindi), प्रश्न and उत्तर are seen as more 'formal' in modern Hindi. So, you would typically use सवाल and जवाब in daily speech but प्रश्न and उत्तर in newspaper articles (of course, this is not a rule). There are cases you would always use one or the other though- for instance, a 'question paper' is always 'प्रश्न पत्र'.