5 students scored a combined total of 92 * 5 = <<92*5=460>>460
4 additional students scored a combined total of 80 * 4 = <<80*4=320>>320
9 students therefore scored a combined total of 460 + 320 = <<460+320=780>>780
We know the total combined score for 10 students must be at least 85 average * 10 students = <<85*10=850>>850
Therefore, the last student must score at least an 850 - 780 = <<850-780=70>>70
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