Question 546949
Let {{{x_1}}} be the score of the lowest test, {{{x_2}}} be the score of the second lowest test, and so forth until {{{x_10}}} is the score of the highest test.  

We have:
{{{(x_1+x_2+x_3+x_4+x_5+x_6+x_7+x_8+x_9+x_10)/10=82}}}
{{{x_1+x_2+x_3+x_4+x_5+x_6+x_7+x_8+x_9+x_10=820}}}      (1)

We also know that 
{{{(x_1+x_2+x_3+x_4+x_5+x_6+x_7+x_8+x_9)/9=80}}}
{{{x_1+x_2+x_3+x_4+x_5+x_6+x_7+x_8+x_9=720}}}           (2)

Equations (1)-(2) leaves:
{{{(x_1+x_2+x_3+x_4+x_5+x_6+x_7+x_8+x_9+x_10)-(x_1+x_2+x_3+x_4+x_5+x_6+x_7+x_8+x_9)=x_10=820-720}}}
{{{x_10=100}}}


Therefore, the highest score is 100%.