Answer:
missing side length = 9
Step-by-step explanation:

a = 6
b = 7
c = missing side





10(2x)+x
21x is the original number
12x is the reversed number
24x is the reversed then doubled number
Set up an equation:
24x=21x+9
3x=9
x=3
The original number is 63 and the reversed number is 36, which then is 72 when doubled.
Question 1. I am assuming you meant 9/16, and in that case, the answer would be 0.5625. 9-16 is -7.
Question 2. 35.7% in decimal form is relative to what the percent is of. 35.7% of a million is different than 35.7% of one.
Question 3. Once again, this is relative as to what. Percentage of the weight of an elephant? It is important to specify in these types of equations.