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 :)
