2.7×8.9+2.1×2.7-2.7=2.7×(8.9+2.1-1)=2.7×10=27
2.7×8点9+2点1×2点7-2点72.7×8.9+2.1×2.7-2.7=2.7×(8.9+2.1-1)=2.7×10=27