Question 1135052
Let B be the cost of a burger.
Let N be the number of burgers in a box.


N * B = $35

(N+8)*(B-.50) = $35

N = 35/B

(35/B+8)*(B-.50) = 35

(35+8B)/B * (B-.50) = 35

(35+8B)/(B-.5) = 35B

(35+8B) =  35B(B-.5)

(35+8B) = 35B^2 - 17.5B

35B^2 -25.5B - 35 = 0

quadratic formula  {{{x = (-(-25.5) +- sqrt( (-25.5)^2-4*35*35 ))/(2*35) }}}

Yields  two answers, but only one is positive (since we're talking about money after all).

Hence the answer is $1.43 per burger.