To find RT, we should use the Segment Addition Postulate. This postulate tells us that, if we have a point between two points, we can add the lengths of the two smaller segments to find the length of the longer segment. In our case, S is between R and T, so we can get the length RT by adding RS and ST.
RT = RS + ST
We know that the length RS is 15 and the length ST is 9. Now, we can use this to calculate RT.
