If CR 4 RA 6 and RS 10 find AB.?

The question, as it appears cannot be answered because there is no information as to what or where AB is. It would seem this is because the questioner did not think it relevant to mention that ABC and RSC are similar triangles. If they are not, then from the information that is given, the question remains unanswerable. However, if they are similar, then AB = 25.