=(-5/6)÷(-19/6)÷【1/24×（-5/4）】-1
=5/6×6/19÷（-5/96）-1
=5/19÷（-5/96）-1
=5/19×（-96/5）-1
=(-96/19)-1
=(-115/19)
=负6又1/19