The sum of all the interior angles in a hexagon is 720°, so if you add up all the angles and then take them away from 720, you'll get your answer:
152 + 85 = 237
237 + 85 = 322
322 + 125 = 447
447 + 135 = 582
So 720 - 582 = 138°, which is your answer. I hope this helps!