Question 850403
The problem itself says that the sum of the numbers were 24,
since getting mean is the sum of the numbers divided by four which is 6.

If x is added the mean will be 7, which means;

{{{(24+x)/(5) = 7}}}
{{{24+x= 35}}}
{{{x=11}}}

Therefore the fifth number is 11. :) 

Thank you!