Value of X is 96° because a straight angle is 180° so you subtract the given angles from 180° to find the missing angles of the triangle.
The total degrees of the three angles of a triangle also adds up to 180°
So once you find the two of the three angles, you can add them and take them from 180° to find the last angle then subtract that from 180° to get X or just realize that the two angles you found and added will be equal to X.