Answer:
x=65
Explanation:
First, we need to find the 2 base angles of the triangle 
105 is adjacent to another angle, and they are on a straight line. Therefore they are supplementary and add to 180 degrees 
105+z=180 
Subtract 105 from both sides 
z=75 
140 is adjacent to another angle, and they are on a straight line. Therefore they are supplementary and add to 180 degrees 
140+y=180 
Subtract 140 from both sides 
y=40
Now, we know the two base angles of the triangle are 40 and 75. The angles in a triangle add to 180 degrees, so 
40+75+x=180 
Combine like terms by adding 40 and 75
115+x=180 
Subtract 115 from both sides 
x=65