There are 1 + 2 + 2 = <<1+2+2=5>>5 rows that are not reserved for the students.
Hence, 10 - 5 = <<10-5=5>>5 rows are reserved for the students.
That is equal to 5 x 15 = <<5*15=75>>75 seats.
But only 75 x 4/5 = <<75*4/5=60>>60 seats are occupied by the students.
Therefore, 75 - 60 = <<75-60=15>>15 seats can be given to the parents.
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