At Jonathan's school, there are 30 seventh graders participating in the school play. Of the students in the seventh grade, 60% are not participating in the school play. How many seventh graders at Jonathan's school are not participating in the school play?

If 60% of the seventh graders are not participating, then 40% are. 30 people = 40%
Thus, 60% = 75 people

45 seventh graders at Jonathan‘s school are not participating in the school play.

Explanation: In Jonathan's school,30 seventh graders are participating in the school play. And 60% are not participating in the school play.
To find the number of seventh graders not participating in the school play, let the total number of seventh graders be N. Number of of seventh graders participating in the school play = 30. Percentage of of seventh graders not participating in the school play = 60%. Percentage of seventh graders participating in school play = 100% - 60% = 40%. This means that 30 seventh graders are 40% of the total seventh graders, N. 40% = 30/N x 100. N = 30/40 x 100 = 75. The number of seventh graders not participating in the school play: = N - 30 = 75 - 30 = 45.
45 seventh graders at Jonathan’s school are not participating in the school play.