im assuming that the x-8 is the denominator for the 4, and that x-4 is the denominator for the 1.
forst find a common denominator by multiplying the other denominator
4(x-4) + 1(x-8) /(x-4)(x-8)
then expand. F.O.I.L the bottom
4x-16 + x - 8x / x^2 -4x -8x +32
collect like terms
5x -24 / x^2 -12x +32