the sum of three angles of triangle of 180 deg. the sum of two of the angles is equal to the third angle and the difference of the two angles is equal to 2/3 th

suppose that :
x = first angle
y = second angle
z = third angle

The sum of three angles of triangle of 180°
So :
x + y + z = 180

The sum of two of the angles is equal to the third angle
So :
x + y = z

The difference of the two angles is equal to 2/3 the third angles
So :
x - y = (2/3) z

subtitute x + y = z
x + y + z = 180
z + z = 180
2z = 180
z = 180/2
z = 90

x + y = z
x + y = 90

x - y = (2/3) z
x - y = (2/3) (90)
x - y = 60 >>> x = 60 + y

subtitute x = 60 + y
x + y = 90
60 + y + y = 90
60 + 2y = 90
2y = 90 - 60
2y = 30
y = 30/2
y = 15

x = 60 + y
x = 60 + 15
x = 75

We got :
x = 75
y = 15
z = 90

So, the angles are 75°, 15°, and 90°