Given:
Number of data (N) =6
Mean (m) =12
Let the 6 observations are given as: x1,x2,x3,x4,x5,x6
So, mean(m) =x1+x2+x3+x4+x5+x66
12=x1+x2+x3+x4+x5+x66.........(1)
Now, If each observation is multiplied by 2
New mean =2x1+2x2+2x3+2x4+2x5+2x66
New mean =2(x1+x2+x3+x4+x5+x66)
New mean =2×12 (from eq 1.)
New mean =24