Dear student,
As the atomic mass of calcium= 40u
Therefore the no. of atoms present in 40g of calcium= 6.023 x 1023atoms
The atomic mass of neon is= 20u
given mass of neon is 40g
The no. of atoms present in 20g neon will be = 6.023 x 1023 atoms
The no. of atoms present in 1g neon will be = 6.023 x 1023 / 20 atoms
Hence the no. of atoms present in 40g of neon = (6.023 x 1023 x 40) / 20 atoms
= 12.046 x 1023 atoms
Regards