含税金额=未税金额+税额
=未税金额+未税金额*税率
=未税金额*(1+税率)
已知含税金额和税率,则未税金额=含税金额/(1+税率)
增值税专用发票的税率是17%,则:增值税税额=未税金额*0.17
=含税金额/(1+0.17)*0.17