answer:
60
work:
the rule for rounding is pretty easy, if the number before you are trying to round up to is 5 or above, round up. if it is 4 or less, round down. (in this case we are using whole numbers, so instead of rounding down, we just stay in the same unit)
so, let's look at the last digit in 57, or 7 is it higher or lower than 5? 7 is higher than 5 - so that means we round up.
the tens unit above 50 is 60, so 60 would be your answer.
hope this helps!