Question 1026130
{{{P(X>=beta) = 0.10}}}

<==> {{{P(Z = (X-mu)/sigma) = P(Z = (X - 65)/20 >= (beta - 65)/20) = 0.10}}}

By referring to a table of standard normal values, we find that

{{{(beta - 65)/20 = 1.285}}}

==> {{{beta = 65+20*1.285 = 90.7}}}, 

==> the minimum score to get an A is 91.