Hello there! A trapezoid is a quadrilateral, and the angles of a quadrilateral have a sum of 360°. We don't know the angle measurement for A, so let's start off by adding the measurements of the other angles together. 117 + 155 + 25 is 297. Now, we subtract that number from 360 to find the angle measurement. 360 - 297 is 63. There. The measurement of angle A is 63°.