4 : 5 : 6
We know that the angles of the triangles add up to 180°
So do this ratio:
4a : 5a : 6a = 180°
4a + 5a + 6a = 180
15a = 180
Divide by 15:

=

15 and 15 cancels out
a = 12
Plug in a:
4a : 5a : 6a
4(12) : 5(12) : 6(12)
48 : 60 : 72
These are the measure of the angles.48°60°72°
check:
48 + 60 + 72 = 180
180 = 180