well, we know that 213.90 includes the 15% gratuity, so if the meal price was say "x", namely that is the 100%, and we add 15% to that, then 100% + 15% = 115%, so 213.90 is really the 115%.
now, if 213.90 is the 115.%, what is "x"? the 100%.

so since we know the meal without the tip is 186 bucks, the tip was then 213.90 - 186 = 27.90.
but they got extra potato wedges with butter and the waitress was wearing her best hat, they added $20 more, so the tip ended up as 27.90 + 20 = 47.90.
now, if the cost of the meal was $186 and that is the 100%, what is 47.90 off of it in percentage?

Answer:
(14 - x) + (4·x - 22) = 3·x - 8
The absolute value of an given number is always positive. So, when adding two to any positive number will always be greater than the number by itself.
True, -8 is a term. Have a great day.
Let same number of hours = x,
since the salary earned is also the same, then
Salary of supervisor A = $25x
Salary of supervisor B = $20(30)+$30(x-30)
Equating
25x=600+30(x-30)
30x-25x=900-600
5x=300
x=60 hours
Check:
Salary of supervisor A = 25*60=1500
Salary of supervisor B = 20*30+30*(60-30)=600+900=1500, ok.