This question is not elaborate.
7 = 3 does not make sense.
Otherwise, do you mean x = 3?
Please revise your question.
8.25% of 55.60 = 4.58700
We round that number to 4.59
(I am assuming the tip is based on the amount of the pretax bill.)
15% of 55.60 = 8.34
So $55.60 + $4.59 + 8.34 = $68.53
The bill would be $68.53.
Ok I will show my work in the comments
1: slope = 2/1 or 2
2: slope = 5/-5
3: slope = 3/2
4: slope = 7/-4
5: slope = 3/5
6: slope = 2/-8
7: slope = 6/2 or 3
8: slope = 2/-4
9: slope = 1/6