12+[

2

5

×0.75+(9

1

2

−△)×3]÷0.3=98
         12+（0.3+28.5-3△）÷0.3=98
            （0.3+28.5-3△）÷0.3=98-12
                         28.8-3△=86×0.3
                         28.8-3△=25.8
                               3△=28.8-25.8
                               3△=3
△=3÷3
△=1
故答案为：1．