Answer: 135° is the unknown angle measure.
Step-by-step explanation: We know a quadrilateral has 4 angles and measure a total of 360°.
To find the unknown angle simply add all the 3 angles and then subtract them from 360°.
Follow the steps:
88° + 82° + 55° = 225°. (Added the 3 angles)
360° - 225° = 135°. (Subtract the sum of the 3 angles from 360 degrees)
