["Find total units: 7 + 4 = 11 units. Each unit = 88 / 11 = 8 students.","Primary = 7 x 8 = 56. Bring:buy = 5:2 so bring lunch (primary) = 5/7 x 56 = 40.","Secondary = 4 x 8 = 32. Bring:buy = 1:3 so bring lunch (secondary) = 1/4 x 32 = 8. Total = 40 + 8 = 48."]