If there are 25 students in the class, then 2/5*25 = <<2/5*25=10>>10 students like maths.
The number of students who don't like math is 25-10 = <<25-10=15>>15 students.
If 1/3 of the students that don't like math like science, then 1/3*15 = <<1/3*15=5>>5 students like science.
The remaining number of students who enjoy history is 15-5 =<<15-5=10>>10
The combined total for the students who want history and maths is 10+10 = <<10+10=20>>20
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