Translation:I do laundry for seventy-one boys.
Proč nemůže být I wash for seventy-one boys. Wy not I wash for seventy-one boys.
To me (native US English), "do the wash" or "do wash" sounds more natural than just "wash." But maybe there are regional differences, or differences between US and other variants of English. But for sure the meaning is the same as "to do laundry."
Thanks for the link. I have added alternatives that use just "wash" (without any reference to laundry or clothes) and "do the wash." But I have a related question. Does prát mean specifically "to launder" (e.g., clothes) or more generally "to wash" (e.g., a floor, car, windows)?
To me (also native US English) 'I wash' is indeed said though less frequently than 'I do the wash' or 'I do laundry'. Since this is a Czech course for English-speakers, I see no downside to accepting this response. People do say it.
Because the Czech numerals work like this, see the Tips and notes. There is another possibility, but sounds a bit strange or bookish: pro sedmdesát jednoho chlapce. It is used much less. But even there you jave jednoho and not jeden, because it is the accusative case.