log xy + 3 log (x/y) + 5 log (y/x)
log xy + 3 log (x/y) + 5 log (y/x) → log xy + log (x/y)3 + log (y/x)5 → log (xyx3y5/(y3x5)) → log (x4y6/(y3x5)) → log (y3/x)
.
Another way