Question 136247
Since the angles are in a 3:3:4 proportion, you can say that one of the angles is 3 times some value, a second angle is also 3 times that same value, and the third angle is 4 times that value, and that the sum of all three angles is 180, so 3x+3x+4x=180 which is to say 10x=180 and finally x=18, just like you have postulated.

That would mean that one of the angles was 3*18=54, the second would be 3*18=54, and the third would be 4*18=72.


54 + 54 + 72 does indeed equal 180.  So, in fact, it does add up.