Question 148574
sum of the angles of a triangle is 180deg.

 let the angle measure of 1st, 2nd & 3rd angles are x, y & z respectively.

        given second angle is three times first i.e  y = 3 * x = 3x ......(1)
 third angle is 12 less than twice the first
   i.e  z = 2* x - 12 = 2x - 12 ............... (2)

  also  x + y + z = 180 .........(3)

 substituting (1) & (2)  in (3)

     x + 3x + 2x -  12 = 180 
         6x - 12 = 180 
          6x = 180 + 12 = 192 
             x = 192 / 6 = 32deg 
 

         y = 3x  = 3 * 32 = 96 deg
       z = 2x - 12 = 2 * 32 - 12 = 64 -12 = 52 deg