Last semester, all of Ms. Nolte's students did projects. One-half of the students in her second-period class investigated fractals, one-fourth of the students in that class did research projects, and the remaining students conducted surveys and analyzed their results. In her third-period class, one-third of the students investigated fractals, one-half of the students did research projects, and the remaining students conducted surveys and analyzed their results. In the seventh-period class, one-fourth of the students investigated fractals, one-sixth of the students did research projects, and the remaining students conducted a survey and analyzed their results. Overall, 22 students investigated fractals, 18 students did research projects, and 22 students conducted surveys. How many students are in each of Ms. Nolte's classes?