that means you owe them 240

i dont knw how u owe 240each?

but if u spend 450 and paid bk 10 each(i.e.20) then it is 470 now plus ur remain 30/- makes it whole get it!

450/2 = 225
225 + 10 = 235
235 * 2 = 470
470 + 30 = 500/- ;)