kill(all)$

van=facebook.com/LearningCalculus$

Log(k,x):=log(x)/log(k);

P:(2*Log(2^(x-1),abs(x)))/Log(2^(x-1),x+7)<=Log(3,x+12)/Log(3,x+7);

num(lhs(P))<=num(rhs(P));

logcontract(%);

x^2 - x -12 = 0;

solve(%,x);