(28+7/8)÷(-7)÷(-4)
=[28÷(-7)+(7/8)÷(-7)]÷(-4)
=[-4-1/8]÷(-4)
=[4+1/8]÷4
=4÷4+1/8÷4
=1+1/8*1/4
=1+1/32
=1又1/32
(28+7/8)÷(-7)÷(-4)
=(28+7/8)÷[(-7)*(-4)]
=(28+7/8)÷28
=28÷28+7/8÷28
=1+7/8*1/28
=1+1/8*1/4
=1+1/32
=1又1/32