8+(-1/4)-5-(-0.25)
=8-0.25-5+0.25
=8-5
=3
(-81)÷二又四分之一+九分之四÷（-16）
=-81÷9/4-4/9÷16
=-81*4/9-4/9÷4÷4
=-9*9*4÷9-4÷9÷4÷4
=-9*4-1÷4÷9
=-36-1/36
=-36又1/36