One of axoims state that there are at least 2 points that lie in the same line.
F(x) = x^2 - 3x - 7
f(-3) = (-3)^ 2 - 3(-3) - 7
f(-3) = 9 + 9 - 7
f(-3) = 18 - 7
f(-3) = 11
The system of equations becomes: s + u = 28 This represent the number of candles sold16s + 10u = 400 This represents the value of the candles sold--------------------- Now all that is left is to solve for s and u. I suggest eliminating one of the two variables. My choice would be eliminating the u terms.