For this one, the best way to answer is to use the question and it will guide us to the answer.
First, you can eliminate two choices:
the problem states that a number minus ten and nine
so you can eliminate B and D because it is 10 minus a number. In math, you can be picky and take the question exactly.
Then, look at the last part, "when decreased by seven." So now look between A and C and see which one is decreasing by 7. Based on that C would be your answer
C) 9(x-10) -7 = 50
Hope this helps!
, is not a mixed fraction. 
is a mixed fraction.
