Answer:
(x+9.4) = 4.09
Step-by-step explanation:
Let the number be x.
Nick adds 9.4 to the number. It means, the number becomes (x+9.4).
He then doubles the result to get an answer of 16.8. It means,
(x+9.4)² = 16.8
(x+9.4) = 4.09
So, this is the required equation for the given information.