Hello! One-third of the remaining people are teachers and there are 21 of them. Percents are parts of 100, and 100 - 70 is 30. 1/3 of of that 30% are teachers, and 10 is 1/3 of 30. 10% of those at the fair are teachers and there are 21 of them. As we see, 10% is 1/10 of 100. For this, all we need to do now is multiply 21 and 10. 21 * 10 is 210. There. A total of 210 people are at the fair.