brilliant.org angle hunting, I can't figure out where the angle 120 is coming from

Question

I really cannot understand where the number 120 is coming from in the solution to this question on brilliant.org

This is part of the solution:

I understand that equilateral triangles have three 60 degree angles and sides which are of equal length, but I can't see how the yellow angle would be 120 - x. Why is it 120? I just can't correlate the number 120 with the structure of the image.

Cheers!

Answer 1

Together, $x$, one of the triangle's angles, and the yellow angle makes a straight line, which is $180^\circ$. The triangle contributes $60^\circ$ to that, so $x$ and the yellow must together contribute the remaining $120^\circ$.

Answer 2

Yellow angle is $(180 - 60 - x)^\circ$.

It is the angle of a striaght line subtract away $x$ and an angle of the equilateral triangle.

$60^\circ$ comes from equilateral triangle.