This is an isosceles triangle, as indicated by the two lines on two sides (they are equal). One angle is 45 degrees, as indicated. We know that the angles of the two equal sides are equal as well. Knowing that all triangles sum up to 180 degrees, we can subtract 45 from 180 and divide by two to get each equal angle.
Here it is:
180-45=135
135 divided by 2 is 67.5.
This means that the value of x is 67.5 degrees.
To check, we can add all of the sums and it should be 180 degrees.
45+67.5+67.5=180
∴ x= 67.5 degrees
