1.25*(8又5分之4-15分之2)+5分之12/6
=5/4*（8+4/5-2/15）+12/5*1/6
=8*5/4+4/5*5/4-2/15*5/4+2/5
=10+1-1/6+2/5
=11-5/30+12/30
=11+7/30
=11又30分之7