“1. 40% of all workers in LA County (10.2 million people) are working for cash; and not paying taxes. This is because they are predominantly illegal immigrants, working without a green card. (Donald Trump was right)”
The entire population of LA County is 10.2 million. The number of “workers” would be somewhat less.
I can find the population broken down six ways to sunday, but no easy way to calculate the 18-64 population.
‘Civilian labor force’ (over 16, listed as employed or unemployed (not including retired or invisible) in LA County is a little over five million.
http://www.labormarketinfo.edd.ca.gov/file/lfmonth/la$pds.pdf