ten times
55
19.
20 times
20 times
19 times
20
11
20 times if you're counting by ones.
100
A spring tide occur's twice a month and 24 times a year.
This is a very ambiguous question. First, by "writing down from 50 to 100" I presume you mean writing down all the whole numbers from 50 to 100 inclusive, that is, including 50 and including 100. Now, if by "how many times will 10 occur" you mean how many of those numbers will be multiples of 10, the answer is 6. If you mean how many times will the 2 digits 1 and 0 occur in that order as consecutive digits in the decimal numeral of a number, the answer is 1 (100 is the only one of those 51 numerals that contains the digit 1 followed by 0).