For the bit i) I was referring to meritnation textbook solutions and I found out that 550 is added why r we adding 550 that to only once shouldn't we subtract it twice?

Dear Student,

In i) part, as the payment has been made by cheque, we had to subtract 550 once. But we have wrongly subtracted it twice. So, now 550 will added once to rectify the error.

Regards