40.25 is 40 1/4 as a decimal
1/2 I guess I don't think you typed in the question correctly. Not trying to be mean.
I think that the missing value is 16m.
I just multiplied two other numbers with 20 and 20 x 16 x 16 = 5120
I hope this was right.
I do not understand the context of your question, you need extra information to find this out like a picture or a word problem.
If the angles equal each other you would have to solve for x when angle 7 and 8 equal each other. SO... based on that, x would equal 15. This means measure of angle 7 would equal 45 and measure of angle 8 would equal 45. This may not be true because I have no idea what you are asking