So mean also translates to average so the mean of 4 numbers is aprox x=average (x+x+x+x)/4=average to increase x by 2 you add 2 x+2=average (x+2+x+2+x+2+x+2)=4=(4x+8)/4=x+2
you would have to increase the sum/total by 8 to make the numbers' averages' go up by 2
