Question 388722
The sum of the three angles is 180° and in this case the one angle plus this angle plus 10° plus twice (this angle and 10° and this angle), hence three times the angle and the angle plus 10°, hence twice the one angle plus 10° is hundred eighty divided by three, or sixty degrees. Sixty degree is twice the first angle plus ten, hence the first angle is twenty-five degrees.
 
The 2nd angle is thirty-five degrees, and the 3rd becomes hundred-eighty minus sixty, hence hundred-twenty.
 
The sum of the 2 first angles is sixty, which is indeed half of the third.
 
In formula this could be written as : let the angles be a,b,c, 
 
the relationships are b=a+10, c=2(a+b)=2(a+a+10)=2(2a+10)=4a+20
 
and a+b+c=a+a+10+4a+20=6a+30 = 180
 
6a = 150 => a = 25°
 
b=35°
 
c=120°