7分之5-12分之5乘7分之5
=5/7-5/12*5/7
=5/7*(1-5/12)
=5/7*7/12
=5/12
25分之12乘98
=12/25*98
=12/25*(100-2)
=12*4-24/25
=48-24/25
=47又25分之1