[误] The number of teachers invited to the Teachers\' Day celebrations this year were larger than that of last

year.

[正] The number of teachers invited to the Teachers\' Day celebrations this year was larger than that of last

year.

注：a number of 是“若干，许多”的意思，后面应该用动词的复数形式;第二个句子内 the number of 中的 number 是“数目”的意思，尽管后面接了复数 teachers，但主语是单数的 number，所以动词须用单数。