Solve each of the following systems of eqautions by the method of cross-multiplication:
x+yxy=2,
x−yxy=6
x=−12,y=14
xa=yb
ax+by=a2+b2
x+ay=b
ax−by=c
xa+yb=2
ax−by=a2−b2
2x-y=6
x-y=2
x+2y+1=0
2x−3y−12=0