This conjecture is false, A and C don't have to be complementary angles.
Let Angle A be 100 and Angle B be 80 degrees. They are supplementary (sum of 180).
Let Angle C be 100 and Angle B is still 80 degrees. They are supplementary.
However, Angle A and Angle C are not complementary (sum of 90).
When your doing tax the tax is 9.25 you divide that by 100
the add that to your price then 12.5 divided by 100 and subtract that from what you ended up with so you should come out with a total of 4.22
2/3(6c+4)-(8c-5)
1) Get rid of the negative signs
New equation (the ones in bold are the changes): 2/3(6c+4)+(-8c)+(5)
2) Use distributive property for the first part by multiplying 2/3*6c= 4c and 2/3*4= 2 2/3
New equation: 4c+2 2/3+ (-8c) + 5
3) Combine like terms: 4c+(-8c)= -4c and 2 2/3+5= 7 2/3
New and simplified equation: -4c+ 7 2/3
