solve (-\frac{1}{3}-\frac{1}{2})A+\frac{1}{3}B =-1,\frac{1}{3}A+(-\frac{1}{3}-\frac{1}{6}-\frac{1}{4})B+\frac{1}{4}D=0,\frac{1}{2} A+\frac{1}{6}B+\frac{1}{5}D=0 for A,B,D