Answer:
100°
Step-by-step explanation:
First, remember that flat angles are always 180°,
So the angle of B is 40° because they form that kind of angle.
Now, you can notice that both sides of the triangle have the same value.
That means the angle is the same too.
So, the third angle is also 40°
Last but not least the addition of all angles in a triangle is always 180°
With that in mind we just solve the next equation:
40° + 40° + a° = 180
a° = |80 - 80
a = 100°
And that is how we find the answer, hope it was helpful ;)