Calculate total sum: A decagon has 10 angles, and the sum of the interior angles of a decagon is (10−2)×180 degrees.Calculate the sum of all angles in the decagon.(10−2)×180=8×180=1440 degrees.
Find sum of remaining angles: Subtract the sum of the seven given angles from the total sum to find the sum of the remaining three angles. 1440 degrees −1086 degrees =354 degrees.
Calculate measure of each angle: Divide the sum of the remaining three angles by 3 to find the measure of each angle since they are equal.354 degrees /3 = 118 degrees.