kill(all)$

van=facebook.com/LearningCalculus$

f(x) := (4*x-5)/(6*x-8) - (8*x^2-96*x+1/6)/(45*x^2-80)
      = (11-10*x)/(9*x+12);

fullratsimp(f(x));

solve(f(x),x);