The measurement of angle x is 35, this is because every triangle equals 180 degrees. I added 51 and 56 degrees together to get 107, then I subtracted 180- 107 to get 73. So 73 degrees is Y, then I added 73 and 72 degrees together to get 145 degrees. Then I subtracted 180- 145 to get the measurement of angle x which is 35.