Answer:

Any expression of the form 
-2/(a+b)
Explanation: you are dividing negative two by the sum of a and b so you would put a+b in parentheses as the denominator and then put -2 as the numerator
0.6n = n + 31.8
0.6n - n = 31.8
-0.4n = 31.8
n = 31.8 / -0.4
n = -79.5
40.47×100=4047 so just multiply it and the the answer is 4047