S阴=SAOED﹣SAOC,
=3×6﹣3×3÷2,
=18﹣4.5,
=13.5(平方厘米);
故答案:13.5平方厘米.
Mr. Zhang is mad at the children who often copy others' homework.
This agreement is very a____(模棱两可的) and open to various interpretations.