41.8, angle y and the measurement angle labeled as just "138.2" are supplementary angles, meaning that when you add them together they equal 180. So all you have to do is subtract 138.2 from 180 and you get your answer which is 41.8.
The wording is a bit strange but I can tell you a ton is 2,000 pounds. 10,500 pounds would be equal to 5.25 tons.
