Solve each of the following systems of eqautions by the method of cross-multiplication:
x+ay=b
ax−by=c
x=ac+b2a2+b,y=ab−ca2+b
xa=yb
ax+by=a2+b2
x+yxy=2,
x−yxy=6
x+2y+1=0
2x−3y−12=0
xa+yb=2
ax−by=a2−b2
ax+by=a-b
bx-ay=a+b