Question 1103850
Let {{{Z}}} be the sum of the other 9 numbers.
The average with 50 would be,
{{{(Z+50)/10}}}
The average without 50 would be,
{{{Z/9}}}
The difference would be,
{{{(Z+50)/10-Z/9=4}}}
{{{9(Z+50)-10Z=360}}}
{{{9Z+450-10Z=360}}}
{{{-Z=-90}}}
{{{Z=90}}}
So then the mean is,
{{{Z/9=90/9}}}
{{{Z/9=10}}}