Which are the 3 angles of the triangle if the second angle is 20 degrees greater than the first and the 3rd angle is twice than the second?

Let's consider the values of the 3
angles:

x = the value in degrees, of the first
angle;

y = the value in degrees, of the second
angle;

z = the value in degree, of the third
angle.

The equation which express the constraint from
enunciation that the second angle is 20 degrees greater than the first angle,
is:

y = x+20, so x = y-20

The
third angle is twice than the second.

z =
2y

We know also that the sum of the angles in a triangle is
180 degrees.

x+y+z = 180

We'll
write each unknown depending on the second angle, y:

y-20 +
y + 2y = 180

4y = 180+20

4y =
200

y = 50
degrees

So, the first angle will
have:

x = y-20

x =
50-20

y = 30
degrees

The third angle is
:

z = 2y

z =
2*50

z = 100
degrees.