Find the amount of atoms for a given mass
For the elements A and B, the relation between the number of atoms n, the mass m, and the atomic mass M is given by


  $$n_A = \frac{m_A}{M_A}\quad,\quad n_B = \frac{m_B}{M_B}$$


Your assignment states:
$$m_B = 2\cdot m_A $$
$$M_B = 2\cdot M_A $$

Solve for $n_B$ ;-)


I seriously suggest to practise these calculations a lot. Ask your tutor for more worksheets or find a workbook (with solutions). Solve it alone, or work in groups. No matter how, you have to practise.

If you are in doubt, where to divide and where to multiply, remember: 

Units are your friends!