Using isosceles triangle theorems solve for x and y

Well lets start by getting y. We already know that all angles of a triangle will equal 180 degrees.
Therefore we know that 65 + 65 + y = 180. To solve for y we just add the two 65's then subtract that from 180
y = 180-130 = 50 Therefore y = 50

Now lets solve for x. We know that since angle B is flat it is equal to 180. The unknown value of angle B = 180 - 65
Therefore that unknown value = 115

As we previously stated all angles of a triangle equal 180. We can now come up with this equation: 115 + x + x = 180
2x = 65
x = 32.5

Hope this helps! If you have anymore questions just ask!

Maybe the answer is 20mm. all i really did was just multiply, which is obvious.