Question 659111
Write what you know as the equation that would be used to calculate an average and then solve for the unknown.

{{{Avg=(86+92+89+88+x)/5}}}
{{{90=(86+92+89+88+x)/5}}}
{{{90*5=((86+92+89+88+x)/5)*5}}}
{{{450=((86+92+89+88+x)}}}
{{{450=355+x}}}
{{{450-355=355+x-355}}}
{{{95=x}}}