Well, the sum of the interior angles of a heptagon is 900°. So, x = ......
First we add all the angles we do know: 139 + 121 + 125 + 126 + 158 + 120.
139 + 121 = 260 260 + 125 = 385 385 + 126 = 511 511 + 158 = 669 669 + 120 = 789
Then, subtract this number from 900:
900 - 789 = 111 Which means that x = 111°!