No,Yes,No,Yes (the answers in order)
Answer:
The missing number would be a 9
Well this isn't college math lol
You do 19x + 13x + 4x = 26x
180 divided by 26x = x = 6.92307...
plug in x then round to tenth
6.9 x 19 = 131.1 degrees
6.9 x 13 = 89.7 degrees
6.9 x 4 = 27.6 degrees
Answer:
No, because both of them will never be able to match; become equivalent. You would have to multiply 2 different numbers to make them match, meaning they would not be proportional. For a comparison to be proportional, the ratio you are trying to simplify to must be achieved by multiplying 2 numbers from the previous ratio by one LCD.

They are<em> able</em> to make 12/21, but that does not mean they are proportional.