Question 548233
One important thing to remember is that all angles sum to 180 degrees. 
Let x be the measure of the third angle.   
Since the second angle is half of the first angle, this is just saying the second angle is {{{75/2=37.5}}}


So we have the sum of all angles is 180:
{{{75+37.5+x=180}}}
Now just solve for x (I will let you do the rest, let me know if you are still unsure)