Here is the set up:
(2/3) ÷ (1/6) = unit rate
You finish.
A giant star is a star with substantially larger radius and luminosity than a main-sequence (or dwarf) star of the same surface temperature. They lie above the main sequence (luminosity class V in the Yerkes spectral classification) on the Hertzsprung–Russell diagram and correspond to luminosity classes II and III.
The correct answer is 120 degrees.
With the bigger triangle you can add all of the angles to get 60 degrees. (35+25)
This leaves you with a 120 degrees angle in the unmarked corner of the triangle. Any horizontal line and any triangle is 180 in total.
So with a 120 degree angle in the corner this leaves us with a 60 angle in the smaller triangle. ( The smaller triangle equals 60 degrees in all corners, it is equalateral ).
X is on a horizontal line and we now know that the one side of the line equals 60 degrees and any horizontal line equals 180 in total, this means that the measure of X is 120, (60+120)
X is 120 :)