The math teacher would be happy if the class average test score was at least 85. There are 10 students in the class, 5 of which scored a 92 on the test and 4 of which scored an 80. What would the last student have to score to at least make the teacher happy?
5 students scored a combined total of 92 * 5 = 
<gadget id="calculator">92*5</gadget>
<output>460</output>
460
4 additional students scored a combined total of 80 * 4 = 
<gadget id="calculator">80*4</gadget>
<output>320</output>
320
9 students therefore scored a combined total of 460 + 320 = 
<gadget id="calculator">460+320</gadget>
<output>780</output>
780.
We know the total combined score for 10 students must be at least 85 average * 10 students = 
<gadget id="calculator">85*10</gadget>
<output>850</output>
850.
Therefore, the last student must score at least an 850 - 780 = 
<gadget id="calculator">850-780</gadget>
<output>70</output>
70.

<result>70</result>