Answer:
Step-by-step explanation:
At the point where two line cut across, the vertically opposite angles formed are equal. This means that
2x degrees = 78 degrees
Dividing the left hand side and the right hand side of the equation by 2, it becomes
2x/2 = 78/2
x = 39
Checking,
The sum of the angles on a straight line is 180 degrees.
180 - 78 = 102 degrees
2x + 102 = 180
2x = 180 - 102 = 78
x = 78/2 = 39
