Answer :
Note: In option c, it must be 34° instead of 340.
Given:
Base angles of an isosceles triangle are represented by x.
The vertex angle is 3x + 10.
To find:
The measure of a base angle.
Solution:
We know that, base angles of an isosceles triangle are equal. So, base angles are x and x.
According to the angle sum property of triangles, the sum of all interior angles of a triangle is 180 degrees.
Using angle sum property of triangles, we get
[tex]x+x+(3x+10)=180[/tex]
[tex]5x=180-10[/tex]
[tex]5x=170[/tex]
Divide both sides by 5.
[tex]x=\dfrac{170}{5}[/tex]
[tex]x=34[/tex]
The measure of base angle is 34 degrees. Therefore the correct option is c.