Since there are 5 angles given, the polygon is a pentagon. Sum of interior angles of a pentagon = (2(5) - 4) x 90^\circ = 540^\circ \(\therefore\) x + 2x + 3x + 4x + 5x = 15x 15x = 540^\circ \(x = \frac{540}{15} = 36^\circ\)