The angles must add to 180 degrees. Since the angles are in the ratio 7:9:4, their measures are not 7, 9, and 4 since 7, 9, and 4 do not add to 180. If you multiply 7, 9, and 4 by the same number, the new numbers will be in the same ratio. Since we do not know what that number is, we can use x for it.
Multiply 7, 9, and 4 by x to get 7x, 9x, and 4x. Now add them and set equal to 180. Then solve for x.
7x + 9x + 4x = 180
20x = 180
x = 9
Now that we know x equals 9, substitute x with 9 and evaluate 7x, 9x, and 4x to find the actual angle measures.
