Answer = 50°
-A triangle adds up to 180°
-A straight line adds up to 180°
Because 105° is on the outer side of that line on the triangle,
We must substract 180° from 105° to get the angle on the inside of the triange (cause it’s a straight line)
which would be 75°
Now add up 75° and 55° = 130°
Since a triangle adds up to 180°,
180° - 130° = 50°
X = 50°