What is the value of x?

x = 30°.

Step-by-step explanation:

To calculate the value of 'x', we can first derive the value of one of the angles that make up the triangle.

Notice that there is an angle with a measure of 100°. The angle that makes up the angle of the triangle is called a Vertical Angle. Therefore, if the angle in red is 100°, the vertical angle, or the third angle of the triangle, is 100°.

There are two congruent sides to the triangle, as seen by the congruent lines. This means that both of the other two angles must be equal. Find the value of 'x' by:

180 - 100 = 80. Since the value of one angle was 100°, and the angles in a triangle must add up to 180°, you can simply subtract to find the sum of the other two angles.

(x + 10) + (x + 10) = 80

2x + 20 = 80

2x = 60

x = 30°.

x intercept = (-1,0)   (4,0)