rhe mean of 8 numbers is 42.if 1 number is excluded,their mean becomes 39.what will be the excluded number?

Mean of 8 nos=42
So,sum of all eight nos.=8*42=336
if one no is excluded, total no of nos=7
given new mean is 39.
sum of the seven nos=39*7=273
no excluded =difference between the sum of eight nos and the sum of seven nos.
=336-273
=63
therefore the no excluded is 63.