Question 285581
Let {{{x}}} = grade on 4th test
{{{(71 + 83 + 96 + x)/4 = 85}}}
{{{(250 + x)/4 = 85}}}
{{{250 + x = 4*85}}}
{{{250 + x = 340}}}
{{{x = 90}}}
He must score 90