the sum of all interior angles in a polygon, is
180(n-2). n = number of sides in the polygon.
now, this polygon has 5 sides, a PENTAgon, therefore the sum is 180( 5 - 2) or 180(3) or 540°.
therefore then,
Q + P + T + S + R = 540
Q + 90 + 115 + 115 + 90 = 540
surely you'd know what Q is.