The sum of all angles of a triangle is 180 grades (or Pi radians).
The angles are in ratio 2:3:7, this means that by naming an angle X we will have:
2*X+ 3*X + 7*X= 180
so, 12*X =180 => X=15
The first angle is 2* X= 30 grades
The second angle is 3*X= 45 grades
The last angle is 7*X=105 grades