I don't have the answer but all you need to do is divide $3.09 by 20 and $2.09 by 12 and see which is less
If they left 15% the tip should be
$11.40, making the total fee $87.40
You have 2 equations here, both already solved for y. Thus, you could eliminate y by equating the two functions. The resulting equation would depend only upon x. Do this. Solve for x. Then, substitute your value for x into either one of the given functions and calculate y. Present your answer in the form (x,y).
w = 50 - 2.5t
Is there a viable solution when time is 30 minutes? No, because by then the tub will be empty.
Hope this Helps!!