well, what variable are you solving for? like if you're solving for x, it would be:
tg is greater than or equal to 0x
 
        
             
        
        
        
Because segments XY and XZ are of equal length, angle Y and angle Z must be congruent.
All inner angles must add to 180 degrees since it's a triangle.
70+70+x=180
140+x=180
x=40
Final answer: D