For my homework I have to work out if these barcodes..?

For my homework I have to work out if these barcodes..?
are correct, but it sais to work them out u must; Take the digits in odd-numbered positions but does that mean add up all the odd numbers or add up the 1st one, 3rd one ect.?

Best answer:

The key word is “position.” You take the 1st, 3rd, etc not caring whether the number itself is odd or even. Just add them if you find them in those places.