The problem is asking for the value of angle $x^\circ$ in a triangle where the other two angles are $60^\circ$ and $100^\circ$.

In a triangle, the sum of the interior angles is always $180^\circ$. This means:

$60^\circ + 100^\circ + x^\circ = 180^\circ$

Now, solving for $x$:

$x = 180^\circ - (60^\circ + 100^\circ) = 180^\circ - 160^\circ = 20^\circ$

Therefore, the value of $x$ is $20^\circ$.

So the correct answer is B. 20.

Would you like further explanation on this, or have any additional questions?

Here are 5 related questions to expand your understanding:

1. What is the sum of interior angles for any polygon?
2. How do we classify a triangle based on its angles?
3. How can you verify the internal angles of a triangle in a more complex geometric figure?
4. What happens if a triangle has two angles equal to $90^\circ$ and $30^\circ$?
5. How does this concept apply to quadrilaterals and other polygons?

Tip: Always remember, for any triangle, the sum of the internal angles will always be $180^\circ$.