-10-f=-6f+10
-f+6f=10+10
5f=20
F=4
From the given picture, we can see that 2 sides are congruen, then the given triangle is an isosceles triangle. In this triangle the base angles are congruent, so we can draw the following picture:
Now, since interior angles of any triangle add up to 180 degrees, we have

By combining similar terms, we get

Then, x is given as

Therefore, the answer is x=90 degrees