△RST is shown below. XU = –2y + 15 and XW = 3y + 5. There is a triangle RST in which V, W and U are the points on the side RS, side ST and side RT respectively. Segment RX is the angle bisectors of angle TRS, segment SX is the angle bisectors of angle RST, and segment TX is the angle bisectors of angle STR. Segment RX, segment SX, and segment TX intersect each other at point X. Segment XV is perpendicular to side RS, segment XW is perpendicular to side ST, and segment XU is perpendicular to side RT. Find the measure of the radius of the inscribed circle of △RST. Enter your answer in the box.