Answer:

Ephraim paid a 22.3% tip, what was his bill before adding the tip?
23.54
Step-by-step explanation:
For this case we assume the following notation:
represent the total paid for the dinner
x represent the amount before adding the tip
f =0.223 represent the fraction of the total amount destined to the tip
Based on this we can create the following relationship between T and x:

And we can solve for x from the previous equation like this:

Taking T common factor we got:

And if we replace we got:

And the amount destined to the tip would be 
And if we add the two values we see that:
23.54+6.75 = 30.29 representing the total cost.
So then the correct answer for the question:
Ephraim paid a 22.3% tip, what was his bill before adding the tip?
23.54