Two electrodes are placed in a calcium chloride solution and a potential difference is maintained between them. If 5.7 1016 Ca2+ ions and 6.5 1016 Cl‾ ions per second move in opposite directions through an imaginary area between the electrodes, what is the current in the solution?

What are " 5.7 1016" and "6.5 1016"? We need moles or any related units to solve this but I am unable to find such.

To get the current, you need to use the formula:

I = \frac{Q}{t}

Q is the charge flowing. You have 5.7x10^16 doubly positively charged ions, and 6.5x10^16 singly negatively charged ions. Find the net charge flow per second and substitute it into the formula. It's pretty straight forward.