Assume the first angle measures X degrees
First angle = X
The second angle measures twice the first, thus
Second angle = 2X
The third angle is 24° more than the first, that is
Third angle = X + 24
The sum of the angles in any triangle must be 180°, thus
X + 2X + X + 24 = 180
Joining like terms
4X + 24 = 180
Subtracting 24 in both sides of the equation
4X = 180 - 24 = 156
Solving for X
X = 156 / 4 = 39
Now we know the first angle is 39°
Second angle = 2X = 78°
Third angle = X + 24 = 39 + 24 = 63°
Let's check:
39° + 78° + 63° = 180°