Answer: When two straight lines intersect, the vertically opposite angles are equal in measure. Therefore, we can write an equation to represent the relationship between the given angles:
140° = x + 40°
To solve for x, we need to isolate it on one side of the equation. We can do this by subtracting 40 from both sides:
140° - 40° = x
Simplifying, we get:
100° = x
Therefore, the value of x is 100.
Explanation: