You are more likely to get a reply if you give your questions context. You add here “it is credited in the case sales which is confusing me” – but that has no context.
When goods are sold for cash – the double entry is: Dr Cash (in hand) Cr Revenue (or Sales)
When cash is banked the double entry is: Dr Bank/Cash at bank Cr Cash (in hand)
So “cash sales of 50,000 was banked” means 50,000 received from cash sales was paid into the bank. It might be recorded simply as: Dr Bank Cr Revenue (i.e. the combined effect of the two journals above)