65 x 10 = 650.

To get what number equals 65 tens, you just
take 65 and put a zero on the right end of it 
and you get 650.

If you wanted to know what number equals 7 tens,
you would just take 7 and put a zero on the end of 
it and you would get 70.

If you wanted to know what number equals 23 tens,
you would just take 23 and put a zero on the end of 
it and you would get 230.

If you wanted to know what number equals 458 tens,
you would just take 458 and put a zero on the end of 
it and you would get 4580.

A quick way to get any number of tens is to write a
zero on the right end of that number. 

Edwin